Multi-layer golf ball having velocity gradient from slower center to faster cover

ABSTRACT

The present invention is directed to multi-layer golf balls having a center, a cover layer, and at least one intermediate layer between the core and the cover layer. The center, the at least one intermediate layer and the cover are constructed to have different initial velocities and COR such that the gradients of initial velocities and COR progress from a slower center to a faster cover.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/773,906, filed Feb. 6, 2004, which is incorporated byreference in its entirety.

FIELD OF THE INVENTION

This invention is related to multi-layer golf balls having a coefficientof restitution gradient that progresses from a slower center to a fastercover.

BACKGROUND OF THE INVENTION

Two-layer golf balls are typically made with a single solid core encasedby a cover. These balls are generally most popular among recreationalgolfers, because they are durable and provide maximum distance.Typically, the solid core is made of polybutadiene cross-linked withzinc diacrylate and/or similar crosslinking agents. The cover materialis a tough, cut-proof blend of one or more materials known as ionomers,such as SURLYN®, sold commercially by DuPont or IOTEK®, soldcommercially by Exxon.

Multi-layer golf balls may have multiple core layers, multipleintermediate layers, and/or multiple cover layers. They tend to overcomesome of the undesirable features of conventional two-layer balls, suchas hard feel and less control, while maintaining the positiveattributes, such as increased initial velocity and distance. Further, itis desirable that multi-layer balls have a “click and feel” similar towound balls.

Additionally, the spin rates of golf balls affect the overall control ofthe balls in accordance to the skill level of the players. Low spinrates provide improved distance, but make golf balls difficult to stopon shorter shots, such as approach shots to greens. High spin ratesallow more skilled players to maximize control of the golf ball, butadversely affect driving distance. To strike a balance between the spinrates and the playing characteristics of golf balls, additional layers,such as intermediate layers, outer core layers and inner cover layersare added to the solid core golf balls to improve the playingcharacteristics of the ball.

The patent literature discloses a number of multi-layer golf balls. U.S.patent application Ser. No. 10/773,906 which is commonly owned andincorporated herein by reference in its entirety, is directed to animproved multi-layer golf ball displaying certain spin profile. The ballhas a generally rigid, thermosetting polybutadiene outer coresurrounding a relatively soft, low compression inner core. The innercore has a hardness that is less than the hardness of the outer core,and a specific gravity that is less than or equal to the specificgravity of the outer core. The inner core and outer core are formulatedto provide a combined overall core compression of greater than about 50.

U.S. patent application Ser. No. 09/853,252, which is commonly owned andincorporated by reference in its entirety, is directed to golf ballshaving a cover comprising three or more layers: an inner cover layer, anouter cover layer, and an intermediate cover layer. The outer coverlayer comprises a composition formed of a reactive liquid material, andthe combination of the thickness of the cover layers is about 0.125inch. Golf balls prepared accordingly can exhibit substantially the sameor higher coefficient of restitution (“COR”), with a decrease incompression or flexural modulus, compared to golf balls of conventionalconstruction. The resultant golf balls typically have a COR of greaterthan about 0.7 and an Atti compression of at least about 40.

U.S. patent application Ser. No. 10/279,506, which is also commonlyowned, and incorporated by reference in its entirety, is directed to agolf ball comprising an inner core, an outer core, and a cover. At leasta layer of the golf ball is made from a low compression, high CORmaterial, and is being supported by a low deformation, high compressionlayer. The resulting golf ball has high COR at high and low impactspeeds and low compression for controlled greenside play.

U.S. Pat. No. 6,645,089 to Tsuoda et al. and U.S. Pub. patentapplication Nos. 2002/0019268 and 2002/0042308 by Tsunoda, et al. aredirected to a golf ball comprising a 6-layer core. The modulus ofelasticity of each layer of the core progresses from lower to highermodulus in the direction from the center to the outermost core layer.

U.S. Pat. No. 6,419,595 to Maruko et al. is directed to a 5-piece golfball comprising a single core and 4 cover layers. The innermost coverlayer has less than 60 Shore D hardness, the next cover layer hasgreater than 45 Shore D hardness, and the outermost cover layer isharder than the third cover layer.

However, there remains a need to provide multi-layer golf balls havingvelocity gradient that progresses from a slower center to a faster coverto match the balls to the players' swing speed.

SUMMARY OF THE INVENTION

This invention is directed to a multi-layer golf ball comprising a core,a cover layer, and at least one intermediate layer between the core andthe cover layer. The ball may have an unlimited number of intermediatelayers, but typically will have from 1 to 8 and each layer of the ballhas a different coefficient of restitution value. The coefficient ofrestitution gradient from the center to the outermost layer is from lowto high, or the initial velocity gradient from the center to the coverlayer is from slow to fast.

For the purposes of this patent, the center is the innermost core layerand any outer core layer will be considered an intermediate layer.

According to the present invention, the center has a COR value of lessthan 0.800, preferably less than 0.780. The center and the firstintermediate layer have a combined COR value of at least 0.500,preferably at least 0.750. The center, the first intermediate layer, andthe second intermediate layer have a combined COR value of at least0.700, more preferably at least 0.760. The golf ball has a combined CORvalue of at least 0.800, preferably at least 0.805.

In another aspect of the invention, for golf balls with four layers ormore the combined COR of a subassembly is 0.003 lower than the combinedCOR of that subassembly plus the next outer layer, preferably 0.005, andmore preferably 0.010. For golf balls with three layers, the COR of theinner two layers is at least 0.015 lower than the COR for all threelayers, and more preferably 0.018 lower and most preferably 0.020 lower.

In a different aspect of the invention, the change in COR is normalizedas the change in COR from one subassembly to the next larger subassemblyin the radial direction per the thickness of the next larger assembly inthe radial direction. For golf balls with four layers or more, thenormalized combined COR of a subassembly is 0.00010 per thousandth of aninch less than the normalized combined COR of that subassembly plus thenext outer layer, preferably 0.00020 per thousandth, and more preferably0.00030 per thousandth. For golf balls with three layers, the normalizedCOR is 0.00020 per thousandth, preferably 0.00030 per thousandth andmore preferably 0.00040 per thousandth.

In another aspect of the invention, the material of each individuallayer taken alone or independent of the subassembly has a coefficient ofrestitution that is higher than or the same as the coefficient ofrestitution of the layer beneath it.

The center of the multi-layer golf ball may comprise any thermoplasticand/or thermosetting polymer(s) including, but not limited to, apolybutadiene, a polyurethane, a polyurea, a highly neutralized polymer,a silicone, a polyolefin, a polyamide, a polyester, a polyether amide, apolyester amide, or a blend thereof, metallocene or other single sitecatalyzed polymers, styenic block copolymers, ionomers, thermoplasticelastomers, fluoropolymers, styrene butadiene rubber, natural orsynthetic polyisoprene, butyl or halobutyl rubber, or blends thereof.

The intermediate layers may comprise a polybutadiene, a polyurethane, apolyurea, a highly neutralized polymer, a silicone, a polyolefin, apolyamide, a polyester, a polyether amide, a polyester amide, or a blendthereof.

The cover layer may comprise a highly neutralized polymer formed from areaction between acid groups on a polymer, a suitable source of cation,and an organic acid or the corresponding salt, and the extent ofneutralization is at least 80%, preferably at least 90%, and morepreferably 100%. Suitable source of cation is selected from magnesium,sodium, zinc, lithium, potassium and calcium, and the organic acid orthe corresponding salt is selected from oleic acid, salt of oleic acid,stearic acid, salt of stearic acid, behenic acid, salt of behenic acidor combination thereof. The cover layer can also be a product of areaction mixture comprising a polybutadiene, a cis-to-trans catalyst, afree radical source, a crosslinking agent, and a filler.

The cover or core layer may also be a product of a reaction mixturecomprising a diene rubber such as polybutadiene, a peroxide initiator,an unsaturated crosslinking agent such as zinc diacrylate, zincmethacrylate, or zinc dimethacrylate optionally a cis-to-trans catalyst,and a filler.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a multi-layer golf ball with a velocity gradient thatchanges from a slower core to a faster cover layer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to multi-layer golf balls having acenter, a cover layer, and at least one intermediate layer between thecenter and the cover layer. As used herein, a golf ball subassemblycomprises at least the center, may further comprise one or more outercore or intermediate layers and the outer cover. A subassembly of anylayer refers to said layer plus all the inner layers that are underneathsaid layer. The center, the intermediate layers and the cover layer areconstructed to have different COR's, and each subassembly is constructedsuch that the gradients of COR progress from a slower center to a fastercover.

Referring to FIG. 1, the multi-layer golf ball (40) comprises a core orcenter (42), a cover layer (46) and intermediate layers (44, 48, and50). The first subassembly is the core (42). The second subassembly isthe combination of the core (42) and the first intermediate layer (44),and so on.

The center has a COR that is slower than any other portions of the ball.Each subassembly has a COR that is faster than the subassemblyunderneath that subassembly, but is not necessarily higher in modulus.Preferably, the outer cover layer has a low modulus but yet high inresilience. In one embodiment, the center is a fluid enclosed in a firstintermediate layer, and the outer cover layer is a highly neutralizedpolymer or a thermosetting polybutadiene formulation comprising ahalogenated organosulfur compound.

The intermediate layers can be mantle layers, outer core layers, orinner cover layers. The multi-layer golf ball preferably has a total of3 to 10 layers, and more preferably 3 to 6 layers but is not limited toany number of layers. Therefore, there is at least one intermediatelayer, and there can be as many as 8 intermediate layers, preferably asmany as 4 intermediate layers. The first intermediate layer is closestto the center. The second intermediate layer is the next intermediatelayer outside of the first intermediate layer.

The coefficient of restitution (“COR”) is a measurement of the collisionbetween the ball and a relatively larger mass. One conventionaltechnique for measuring COR uses a golf ball or golf ball subassembly,air cannon, and a stationary vertical steel plate. The steel plateprovides an impact surface weighing about 100 pounds or about 45kilograms. A pair of ballistic light screens are spaced apart andlocated between the air cannon and the steel plate. The ball is firedfrom the air cannon toward the steel plate over a range of testvelocities from 50 ft/sec to 180 ft/sec. Unless noted otherwise, all CORdata presented in this application are measured using a speed of 125ft/sec. As the ball travels toward the steel plate, it activates eachlight screen so that the time at each light screen is measured. Thisprovides an incoming time period proportional to the ball's incomingvelocity. The ball impacts the steel plate and rebounds though the lightscreens, which again measure the time period required to transit betweenthe light screens. This provides an outgoing transit time periodproportional to the ball's outgoing velocity. The COR can be calculatedby the ratio of the outgoing transit time period to the incoming transittime period.

As discussed above, the initial velocity of each subassembly is lessthan, or about equal to, the next larger subassembly toward the cover.The center has a COR (COR_(C)) that is slowest among all thesubassemblies. The center and the first intermediate layer subassemblyhas an COR (COR_(C1)) that is faster than, or about equal to, the COR(COR_(C)) of the center. Likewise, the center, and the first and secondintermediate layers have an COR (COR_(C2)) that is faster than, or aboutequal to, the COR of the center and the first intermediate layer.

At 125 ft/sec, the COR of the center (COR_(C1)) is less than 0.800,preferably less than 0.780. The combined COR (COR_(C1)) of the centerand the first intermediate layer is greater than the COR (COR_(C)) ofthe center. COR_(C1) is at least 0.780, preferably at least 0.790. Thecombined COR (COR_(C2)) of the center, and the first and secondintermediate layers is faster than the COR (COR_(C1)) of the center andthe first intermediate layer. COR_(C2) is at least 0.790, preferably atleast 0.800. For golf balls with four or more layers, the COR of eachsubassembly is at least about 0.003 less than the next largersubassembly toward the cover, preferably at least about 0.005 less, andmore preferably at least about 0.010 less. For golf balls with threelayers, the COR of each subassembly is at least about 0.015 less thanthe next larger subassembly, preferably at least about 0.018 and morepreferably at least about 0.020.

Consequently, the multi-layer golf ball has an initial velocity or CORgradients that progress from a slower center to a faster cover. Theinitial velocity gradient from the center to the cover can be expressedby:V _(C) ≦V _(C1) ≦V _(C2) ≦V _(C3) ≦V _(C4) ≦V _(C5) . . .When the ball has four or more layers, the COR gradient can be expressedby:COR _(C) ≦COR _(C1)−0.003; COR _(C1) ≦COR _(C2)−0.003; COR _(C2) ≦COR_(C3)−0.003 . . .When the ball has three layers, the COR gradient can be expressed by:COR _(C) ≦COR _(C1)−0.015; COR _(C1) ≦COR _(C2)−0.015.

In another embodiment, the velocity gradient is normalized per layerthickness in the radial direction such that a “normalized COR” isdefined as the change in COR from one subassembly to the next largersubassembly in the radial direction divided by the thickness of the nextsubassembly, wherein the value reported is defined as the COR change perthousandth of an inch. For golf balls with four layers or more, thenormalized COR is at least 0.00010, preferably 0.00020 and morepreferably 0.00030. For golf balls with three layers, the normalized CORis at least 0.00020, preferably 0.00030 and more preferably 0.00040.

In one embodiment, a golf ball has so constructed a COR of less thanabout 0.820 and an initial velocity conforming to current USGA limits.

In a different embodiment, the material of each individual layer, takenby itself, has a coefficient of restitution greater than or equal to thematerial of the layer beneath it. Coefficient of restitution of thematerial may be defined as the COR of a sphere between 0.25 inch to 1.68inch, preferably between 1.00 inch to 1.62 and more preferably between1.30 inch to 1.60 inch molded of that material and that sphere is testedfor COR as discussed above. The COR of the material can also be measuredon a plaque, button, or slab of material such as bayshore resilience,tan delta via dynamic mechanical analysis. A method of measuringcoefficient of restitution is described in commonly-owned U.S. patentapplication Ser. No. 10/914,289, which is incorporated herein byreference in its entirety. At 125 ft/sec, the coefficient of restitutionof the materials according to this invention, as defined in COR values,may be in the range of about 0.500 to about 0.990, preferably about0.700 to about 0.900, and more preferably about 0.750 to about 0.850.The COR of the material used to create a layer (center, outer core,intermediate layer, inner or outer cover, etc.) is then “extrapolated”or otherwise standardized to the COR of standard spheres, and the sameequations used for the composite subassemblies, discussed above, areused for “material COR”. For example for a four-layer ball constructionsolid spheres at a size of 1.500 inch are molded using the materialsused for the center, outer core, inner cover, other intermediate layersand outer cover, respectively. The relationship of CORs is such that theCOR of the inner core<COR of the next layer<COR of the next layer<COR ofthe outer cover.

Compression is an important factor in golf ball design, e.g. thecompression of the center, and intermediate layers helps determine theball's spin rate off the driver and the feel. Several different methodshave been used to measure compression, including Atti compression,Riehle compression, load/deflection measurements at a variety of fixedloads and offsets, and the effective modulus. See Jeff Dalton,Compression by Any Other Name, Science and Golf IV, Proceedings of theWorld Scientific Congress of Golf (Eric Thain ed., Routledge, 2002) (“J.Dalton”). The conversions from the Atti compression to Riehle (cores),Riehle (balls), 100 kg deflection, 130-10 kg deflection or effectivemodulus can be carried out according to the formulas given in J. Dalton.Likewise, the golf balls of this invention are not constrained to aparticular progression of flexural modulus, hardness or compression.Coating or paint layers on the balls' dimpled surface are not consideredas pieces or layers of the constructions discussed herein. Nor are“adhesive layers” such as those disclosed in U.S. Pat. Nos. 6,746,345,6,736,737, 6,723,008, 6,702,695, and 6,652,392. Generally any layer lessor equal to 0.002″ is not considered a piece or layer of theconstruction herein.

The center of the multi-layer golf ball may comprise a fluid (gas orliquid) filled core such as that described in 10/670,514, and U.S. Pat.No. 6,632,147, both are incorporated by reference in their entireties.Suitable fluids usable in the centers in accordance with their specificgravities include air, other gases, aqueous solutions, liquids, gels,foams, hot-melts, other fluid materials and combinations thereof.Examples of suitable liquids include either solutions such as salt inwater, corn syrup, salt in water and corn syrup, glycol and water oroils. The liquid can further include pastes, colloidal suspensions, suchas clay, barytes, water or other liquid, or salt in water/glycolmixtures. Examples of suitable gels include water gelatin gels,hydrogels, water/methyl cellulose gels and gels comprised of copolymerrubber based materials such a styrene-butadiene-styrene rubber andparaffinic and/or naphthenic oil. Examples of suitable melts includewaxes and hot melts. Hot-melts are materials, which at or about normalroom temperatures are solid but at elevated temperatures become liquid.A high melting temperature is desirable since the liquid core is heatedto high temperatures during the molding of the inner core, outer core,and the cover. Alternatively, the liquid can be a selective reactiveliquid system, which combines to form a solid. Examples of suitablereactive liquids are silicate gels, agar gels, peroxide cured polyesterresins, two part epoxy resin systems, peroxide cured liquidpolybutadiene rubber compositions, reactive polyurethanes, silicones andpolyesters. Additionally, suitable fluids also include low specificgravity liquid such as petroleum, vegetable or animal based oils,methanol, ethanol, ammonia, etc., or a high specific gravity liquid suchas glycerin or carbon tetrachloride.

The center may also comprise thermosetting or thermoplastic materialssuch as polyurethane, polyurea, partially or fully neutralized ionomers,thermosetting polydiene rubber such as polybutadiene, polyisoprene,ethylene propylene diene monomer rubber, ethylene propylene rubber,natural rubber, balata, butyl rubber, halobutyl rubber, styrenebutadiene rubber or any styrenic block copolymer such as styreneethylene butadiene styrene rubber, etc., metallocene or other singlesite catalyzed polyolefin, polyurethane copolymers, e.g. with silicone,as long as the material meets the COR criteria described above.

In addition to the materials discussed above, compositions within thescope of the present invention can incorporate one or more polymers.Examples of suitable additional polymers for use in the presentinvention include, but are not limited to, the following: thermoplasticelastomer, thermoset elastomer, synthetic rubber, thermoplasticvulcanizate, copolymeric ionomer, terpolymeric ionomer, polycarbonate,polyolefin, polyamide, copolymeric polyamide, polyesters, polyvinylalcohols, acrylonitrile-butadiene-styrene copolymers, polyarylate,polyacrylate, polyphenylene ether, impact-modified polyphenylene ether,high impact polystyrene, diallyl phthalate polymer, metallocenecatalyzed polymers, styrene-acrylonitrile (SAN) (includingolefin-modified SAN and acrylonitrile-styrene-acrylonitrile),styrene-maleic anhydride (S/MA) polymer, styrenic copolymer,functionalized styrenic copolymer, functionalized styrenic terpolymer,styrenic terpolymer, cellulose polymer, liquid crystal polymer (LCP),ethylene-propylene-diene terpolymer (EPDM), ethylene-vinyl acetatecopolymers (EVA), ethylene-propylene copolymer, ethylene vinyl acetate,polyurea, and polysiloxane or any metallocene-catalyzed polymers ofthese species. Suitable polyamides for use as an additional material incompositions within the scope of the present invention also includeresins obtained by: (1) polycondensation of (a) a dicarboxylic acid,such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine or decamethylenediamine,1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as .epsilon.-caprolactam oromega.-laurolactam; (3) polycondensation of an aminocarboxylic acid,such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoicacid or 12-aminododecanoic acid; or (4) copolymerization of a cycliclactam with a dicarboxylic acid and a diamine. Specific examples ofsuitable polyamides include Nylon 6, Nylon 66, Nylon 610, Nylon 11,Nylon 12, copolymerized Nylon, Nylon MXD6, and Nylon 46.

Other preferred materials suitable for use as an additional material incompositions within the scope of the present invention include polyesterelastomers marketed under the tradename SKYPEL by SK Chemicals of SouthKorea, or diblock or triblock copolymers marketed under the tradenameSEPTON by Kuraray Corporation of Kurashiki, Japan, and KRATON by KratonPolymers Group of Companies of Chester, United Kingdom. All of thematerials listed above can provide for particular enhancements to balllayers prepared within the scope of the present invention.

Ionomers also are well suited for blending into compositions within thescope of the present invention. Suitable ionomeric polymers (i.e.,copolymer- or terpolymer-type ionomers) include.alpha.-olefin/unsaturate- d carboxylic acid copolymer-type ionomeric orterpolymer-type ionomeric resins. Copolymeric ionomers are obtained byneutralizing at least a portion of the carboxylic groups in a copolymerof an .alpha.-olefin and an .alpha.,.beta.-unsaturated carboxylic acidhaving 3 to 8 carbon atoms, with a metal ion. Examples of suitablealpha.-olefins include ethylene, propylene, 1-butene, and 1-hexene.Examples of suitable unsaturated carboxylic acids include acrylic,methacrylic, ethacrylic, .alpha.-chloroacrylic, crotonic, maleic,fumaric, and itaconic acid. Copolymeric ionomers include ionomers havingvaried acid contents and degrees of acid neutralization, neutralized bymonovalent or bivalent cations discussed above.

Terpolymeric ionomers are obtained by neutralizing at least a portion ofcarboxylic groups in a terpolymer of an .alpha.-olefin, and an.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon atoms,and an .alpha.,.beta.-unsaturated carboxylate having 2 to 22 carbonatoms with metal ion. Examples of suitable .alpha.-olefins includeethylene, propylene, 1-butene, and 1-hexene. Examples of suitableunsaturated carboxylic acids include acrylic, methacrylic, ethacrylic,.alpha.-chloroacrylic, crotonic, maleic, fumaric, and itaconic acid.Terpolymeric ionomers include ionomers having varied acid contents anddegrees of acid neutralization, neutralized by monovalent or bivalentcations as discussed above. Examples of suitable ionomeric resinsinclude those marketed under the name SURLYN® manufactured by E.I. duPont de Nemours & Company of Wilmington, Del., and IOTEK® manufacturedby Exxon Mobil Corporation of Irving, Tex.

Silicone materials also are well suited for blending into compositionswithin the scope of the present invention. These can be monomers,oligomers, prepolymers, or polymers, with or without additionalreinforcing filler. One type of silicone material that is suitable canincorporate at least 1 alkenyl group having at least 2 carbon atoms intheir molecules. Examples of these alkenyl groups include, but are notlimited to, vinyl, allyl, butenyl, pentenyl, hexenyl and decenyl. Thealkenyl functionality can be located at any location of the siliconestructure, including one or both terminals of the structure. Theremaining (i.e., non-alkenyl) silicon-bonded organic groups in thiscomponent are independently selected from hydrocarbon or halogenatedhydrocarbon groups that contain no aliphatic unsaturation. Non-limitingexamples of these include: alkyl groups, such as methyl, ethyl, propyl,butyl, pentyl and hexyl; cycloalkyl groups, such as cyclohexyl andcycloheptyl; aryl groups, such as phenyl, tolyl and xylyl; aralkylgroups, such as benzyl and phenethyl, and halogenated alkyl groups, suchas 3,3,3-trifluoropropyl and chloromethyl. Another type of siliconematerial suitable for use in the present invention is one havinghydrocarbon groups that lack aliphatic unsaturation. Specific examplesof suitable silicones for use in making compositions of the presentinvention include the following: trimethylsiloxy-endblockeddimethylsiloxane-methylhexenylsiloxane copolymers;dimethylhexenlylsiloxy-endblocked dimethylsiloxane-methylhexenylsiloxanecopolymers; trimethylsiloxy-endblockeddimethylsiloxane-methylvinylsiloxa- ne copolymers;trimethylsiloxy-endblocked methylphenylsiloxane-dimethylsil-oxane-methylvinylsiloxane copolymers; dimethylvinylsiloxy-endblockeddimethylpolysiloxanes; dimethylvinylsiloxy-endblockeddimethylsiloxane-methylvinylsiloxane copolymers;dimethylvinylsiloxy-endblocked methylphenylpolysiloxanes;dimethylvinylsiloxy-endblockedmethylphenylsiloxane-dimethylsiloxane-methylvinylsiloxane copolymers;and the copolymers listed above, in which at least one end group isdimethylhydroxysiloxy. Commercially available silicones suitable for usein compositions within the scope of the present invention includeSilastic by Dow Coming Corp. of Midland, Mich., Blensil by GE Siliconesof Waterford, N.Y., and Elastosil by Wacker Silicones of Adrian, Mich.

Other types of copolymers also can be added to compositions within thescope of the present invention. Examples of copolymers comprising epoxymonomers and which are suitable for use within the scope of the presentinvention include styrene-butadiene-styrene block copolymers, in whichthe polybutadiene block contains an epoxy group, andstyrene-isoprene-styrene block copolymers, in which the polyisopreneblock contains epoxy. Commercially available examples of these epoxyfunctional copolymers include ESBS A1005, ESBS A1010, ESBS A1020, ESBSAT018, and ESBS AT019, marketed by Daicel Chemical Industries, Ltd. ofOsaka, Japan.

A preferred embodiment for a slow core comprises polybutadiene, SBR,little or no zinc diacrylate (from 0-10 parts), optional zincdimethacrylate, or a non zinc salt unsatured monomer such as trimethylolpropane triacrylate (SR-350 sold by the Sartomer Co.), a peroxideinitiator. Other formulations for the core are disclosed in co-pendingcommonly owned application Ser. No. 10/845,721, which is incorporatedherein by reference in its entirety. Alternatively, a non-peroxide,sulfur vulcanized formulation, such as that disclosed in pending U.S.application Ser. No. 10/772,689 can be used. This reference isincorporated by reference herein in its entirety.

The core diameter ranges from about 0.100 inch to about 1.64 inch,preferably from about 1.00 inch to about 1.62 inch. Typical corediameter ranges from 0.25 inch to 1.625 inch in increments of 0.05 inch.Common core sizes are 0.050 inch, 1.00 inch 1.10 inches, 1.20 inches,1.30 inches, 1.40 inches, 1.45 inches, 1.50 inches 1.55 inches. 1.57inches, 1.58 inches, 1.59 inches and 1.60 inches. That is, the sizes ofthe core plus any intermediate layer or layers may be within the samesize or size range as the core sizes above.

Other suitable materials for the core include, but are not limited to:

-   -   (1) Polyurethanes, such as those prepared from polyols and        diisocyanates or polyisocyanates and those disclosed in U.S.        Pat. Nos. 5,334,673 and 6,506,851 and U.S. patent application        Ser. No. 10/194,059;    -   (2) Polyureas, such as those disclosed in U.S. Pat. No.        5,484,870 and U.S. patent application Ser. No. 10/228,311; and    -   (3) Polyurethane-urea hybrids, blends or copolymers comprising        urethane or urea segments.

The core of the multi-layer golf ball preferably includes a polyurethanecomposition comprising the reaction product of at least onepolyisocyanate and at least one curing agent. The curing agent caninclude, for example, one or more diamines, one or more polyols, or acombination thereof. The polyisocyanate can be combined with one or morepolyols to form a prepolymer, which is then combined with the at leastone curing agent. Thus, the polyols described herein are suitable foruse in one or both components of the polyurethane material, i.e., aspart of a prepolymer and in the curing agent.

The center or any layer in the golf ball can also be made fromhighly-neutralized polymers and blends thereof (“HNP”). The acidmoieties of the HNP's, typically ethylene-based ionomers, are preferablyneutralized greater than about 70%, more preferably greater than about90%, and most preferably at least about 100%. The HNP's can be also beblended with a second polymer component, which, if containing an acidgroup, may be neutralized in a conventional manner, by the organic fattyacids of the present invention, or both. The second polymer component,which may be partially or fully neutralized, preferably comprisesionomeric copolymers and terpolymers, ionomer precursors,thermoplastics, polyamides, polycarbonates, polyesters, polyurethanes,polyureas, thermoplastic elastomers, polybutadiene rubber, balata,metallocene-catalyzed polymers (grafted and non-grafted), single-sitepolymers, high-crystalline acid polymers, cationic ionomers, and thelike. HNP polymers typically have a material hardness of between about20 and about 80 Shore D, and a flexural modulus of between about 3,000psi and about 200,000 psi.

In one embodiment of the present invention the HNP's are ionomers and/ortheir acid precursors that are preferably neutralized, either filly orpartially, with organic acid copolymers or the salts thereof. The acidcopolymers are preferably α-olefin, such as ethylene, C₃₋₈α,β-ethylenically unsaturated carboxylic acid, such as acrylic andmethacrylic acid, copolymers. They may optionally contain a softeningmonomer, such as alkyl acrylate and alkyl methacrylate, wherein thealkyl groups have from 1 to 8 carbon atoms.

The acid copolymers can be described as E/X/Y copolymers where E isethylene, X is an α,β-ethylenically unsaturated carboxylic acid, and Yis a softening comonomer. In a preferred embodiment, X is acrylic ormethacrylic acid and Y is a C₁₋₈ alkyl acrylate or methacrylate ester. Xis preferably present in an amount from about 1 to about 35 weightpercent of the polymer, more preferably from about 5 to about 30 weightpercent of the polymer, and most preferably from about 10 to about 20weight percent of the polymer. Y is preferably present in an amount fromabout 0 to about 50 weight percent of the polymer, more preferably fromabout 5 to about 25 weight percent of the polymer, and most preferablyfrom about 10 to about 20 weight percent of the polymer.

Specific acid-containing ethylene copolymers include, but are notlimited to, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate,ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylicacid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate,ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/methacrylic acid/methyl methacrylate, andethylene/acrylic acid/n-butyl methacrylate. Preferred acid-containingethylene copolymers include, ethylene/methacrylic acid/n-butyl acrylate,ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/acrylic acid/ethyl acrylate, ethylene/methacrylicacid/ethyl acrylate, and ethylene/acrylic acid/methyl acrylatecopolymers. The most preferred acid-containing ethylene copolymers are,ethylene/(meth) acrylic acid/n-butyl, acrylate, ethylene/(meth)acrylicacid/ethyl acrylate, and ethylene/(meth) acrylic acid/methyl acrylatecopolymers.

Ionomers are typically neutralized with a metal cation, such as Li, Na,Mg, or Zn. It has been found that by adding sufficient organic acid orsalt of organic acid, along with a suitable base, to the acid copolymeror ionomer, however, the ionomer can be neutralized, without losingprocessability, to a level much greater than for a metal cation.Preferably, the acid moieties are neutralized greater than about 80%,preferably from 90-100%, most preferably 100% without losingprocessability. This is accomplished by melt-blending an ethyleneα,β-ethylenically unsaturated carboxylic acid copolymer, for example,with an organic acid or a salt of organic acid, and adding a sufficientamount of a cation source to increase the level of neutralization of allthe acid moieties (including those in the acid copolymer and in theorganic acid) to greater than 90%, (preferably greater than 100%).

The organic acids of the present invention are aliphatic, mono- ormulti-functional (saturated, unsaturated, or multi-unsaturated) organicacids. Salts of these organic acids may also be employed. The salts oforganic acids of the present invention include the salts of barium,lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium,strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver,aluminum, tin, or calcium, salts of fatty acids, particularly stearic,bebenic, erucic, oleic, linoelic or dimerized derivatives thereof. It ispreferred that the organic acids and salts of the present invention berelatively non-migratory (they do not bloom to the surface of thepolymer under ambient temperatures) and non-volatile (they do notvolatilize at temperatures required for melt-blending).

The ionomers of the invention may also be partially neutralized withmetal cations. The acid moiety in the acid copolymer is neutralizedabout 1 to about 100%, preferably at least about 40 to about 100%, andmore preferably at least about 90 to about 100%, to form an ionomer by acation such as lithium, sodium, potassium, magnesium, calcium, barium,lead, tin, zinc, aluminum, or a mixture thereof.

The acid copolymers of the present invention are prepared from ‘direct’acid copolymers, copolymers polymerized by adding all monomerssimultaneously, or by grafting of at least one acid-containing monomeronto an existing polymer.

Thermoplastic polymer components, such as copolyetheresters,copolyesteresters, copolyetheramides, elastomeric polyolefins, styrenediene block copolymers and their hydrogenated derivatives,copolyesteramides, thermoplastic polyurethanes, such ascopolyetherurethanes, copolyesterurethanes, copolyureaurethanes,copolyureaurethaneas, epoxy-based polyurethanes, polycaprolactone-basedpolyurethanes, polyureas, and polycarbonate-based polyurethanes fillers,and other ingredients, if included, can be blended in either before,during, or after the acid moieties are neutralized, thermoplasticpolyurethanes.

The copolyetheresters are comprised of a multiplicity of recurring longchain units and short chain units joined head-to-tail through esterlinkages, the long chain units being represented by the formula:

and the short chain units being represented by the formula:

where G is a divalent radical remaining after the removal of terminalhydroxyl groups from a poly (alkylene oxide) glycol having a molecularweight of about 400-8000 and a carbon to oxygen ratio of about 2.0-4.3;R is a divalent radical remaining after removal of hydroxyl groups froma diol having a molecular weight less than about 250; provided saidshort chain ester units amount to about 15-95 percent by weight of saidcopolyetherester. The preferred copolyetherester polymers are thosewhere the polyether segment is obtained by polymerization oftetrahydrofuran and the polyester segment is obtained by polymerizationof tetramethylene glycol and phthalic acid. For purposes of theinvention, the molar ether:ester ratio can vary from 90:10 to 10:80;preferably 80:20 to 60:40; and the Shore D hardness is less than 70;preferably less than about 40.

The copolyetheramides are comprised of a linear and regular chain ofrigid polyamide segments and flexible polyether segments, as representedby the general formula:

wherein PA is a linear saturated aliphatic polyamide sequence formedfrom a lactam or amino acid having a hydrocarbon chain containing 4 to14 carbon atoms or from an aliphatic C₆-C₈ diamine, in the presence of achain-limiting aliphatic carboxylic diacid having 4-20 carbon atoms;said polyamide having an average molecular weight between 300 and15,000; and PB is a polyoxyalkylene sequence formed from linear orbranched aliphatic polyoxyalkylene glycols, mixtures thereof orcopolyethers derived therefrom, said polyoxyalkylene glycols having amolecular weight of less than or equal to 6000; and n indicates asufficient number of repeating units so that said polyetheramidecopolymer has an intrinsic viscosity of from about 0.6 to about 2.05.The preparation of these polyetheramides comprises the step of reactinga dicarboxylic polyamide, the COOH groups of which are located at thechain ends, with a polyoxyalkylene glycol hydroxylated at the chainends, in the presence of a catalyst such as a tetra-alkyl ortho titanatehaving the general formula Ti(OR)_(x) wherein R is a linear branchedaliphatic hydrocarbon radical having 1 to 24 carbon atoms. Again, themore polyether units incorporated into the copolyetheramide, the softerthe polymer. The ether:amide ratios are as described above for theether:ester ratios, as is the Shore D hardness.

The elastomeric polyolefins are polymers composed of ethylene and higherprimary olefins such as propylene, hexene, octene, and optionally1,4-hexadiene and or ethylidene norbomene or norbomadiene. Theelastomeric polyolefins can be optionally functionalized with maleicanhydride, epoxy, hydroxy, amine, carboxylic acid, sulfonic acid, orthiol groups.

Thermoplastic polyurethanes are linear or slightly chain branchedpolymers consisting of hard blocks and soft elastomeric blocks. They areproduced by reacting soft hydroxy terminated elastomeric polyethers orpolyesters with diisocyanates, such as methylene diisocyanate (“MDI”),ρ-phenylene diisocyanate (“PPDI”), or toluene diisocyanate (“TDI”).These polymers can be chain extended with glycols, secondary diamines,diacids, or amino alcohols. The reaction products of the isocyanates andthe alcohols are called urethanes and these blocks are relatively hardand high melting. These hard high melting blocks are responsible for thethermoplastic nature of the polyurethanes.

Block styrene diene copolymers and their hydrogenated derivatives arecomposed of polystyrene units and polydiene units. They may also befunctionalized with moieties such as OH, NH₂, epoxy, COOH, and anhydridegroups. The polydiene units are derived from polybutadiene, polyisopreneunits or copolymers of these two. In the case of the copolymer it ispossible to hydrogenate the polyolefin to give a saturated rubberybackbone segments. These materials are usually referred to as SBS, SIS,or SEBS thermoplastic elastomers and they can also be functionalizedwith maleic anhydride.

Grafted metallocene-catalyzed polymers are also useful for blending withthe HNP's of the present invention. The grafted metallocene-catalyzedpolymers, while conventionally neutralized with metal cations, may alsobe neutralized, either partially for fully, with organic acids or saltsthereof and an appropriate base. Grafted metallocene-catalyzed polymersuseful, such as those disclosed in U.S. Pat. Nos. 5,703,166; 5,824,746;5,981,658; and 6,025,442, which are incorporated herein by reference, inthe golf balls of the invention are available in experimental quantitiesfrom DuPont under the tradenames SURLYN® NMO 525D, SURLYN® NMO 524D, andSURLYN® NMO 499D, all formerly known as the FUSABOND® family ofpolymers, or may be obtained by subjecting a non-graftedmetallocene-catalyzed polymer to a post-polymerization reaction toprovide a grafted metallocene-catalyzed polymer with the desired pendantgroup or groups. Examples of metallocene-catalyzed polymers to whichfunctional groups may be grafted for use in the invention include, butare not limited to, homopolymers of ethylene and copolymers of ethyleneand a second olefin, preferably, propylene, butene, pentene, hexene,heptene, octene, and norbomene. Generally, the invention includes golfballs having at least one layer comprising at least one graftedmetallocene-catalyzed polymer or polymer blend, where the graftedmetallocene-catalyzed polymer is produced by grafting a functional grouponto a metallocene-catalyzed polymer having the formula:

wherein R₁ is hydrogen, branched or straight chain alkyl such as methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, carbocyclic, oraromatic; R₂ is hydrogen, lower alkyl including C₁-C₅; carbocyclic, oraromatic; R₃ is hydrogen, lower alkyl including C₁-C₅, carbocyclic, oraromatic; R₄ is selected from the group consisting of H, C_(n)H_(2n+1),where n=1 to 18, and phenyl, in which from 0 to 5 H within R₄ can bereplaced by substituents COOH, SO₃H, NH₂, F, Cl, Br, I, OH, SH,silicone, lower alkyl esters and lower alkyl ethers, with the provisothat R₃ and R₄ can be combined to form a bicyclic ring; R₅ is hydrogen,lower alkyl including C₁-C₅, carbocyclic, or aromatic; R₆ is hydrogen,lower alkyl including C₁-C₅, carbocyclic, or aromatic; and wherein x, yand z are the relative percentages of each co-monomer. X can range fromabout 1 to 99 percent or more preferably from about 10 to about 70percent and most preferred, from about 10 to 50 percent. Y can be from99 to 1 percent, preferably, from 90 to 30 percent, or most preferably,90 to 50 percent. Z can range from about 0 to about 49 percent. One ofordinary skill in the art would understand that if an acid moiety ispresent as a ligand in the above polymer that it may be neutralized upto 100% with an organic fatty acid as described above.

Metallocene-catalyzed copolymers or terpolymers can be random or blockand may be isotactic, syndiotactic, or atactic. The pendant groupscreating the isotactic, syndiotactic, or atactic polymers are chosen todetermine the interactions between the different polymer chains makingup the resin to control the final properties of the resins used in golfball covers, centers, or intermediate layers. As will be clear to thoseskilled in the art, grafted metallocene-catalyzed polymers useful in theinvention that are formed from metallocene-catalyzed random or blockcopolymers or terpolymers will also be random or block copolymers orterpolymers, and will have the same tacticity of themetallocene-catalyzed polymer backbone.

As used herein, the term “phrase branched or straight chain alkyl” meansany substituted or unsubstituted acyclic carbon-containing compounds.Examples of alkyl groups include lower alkyl, for example, methyl,ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or t-butyl; upper alkyl,for example, octyl, nonyl, decyl, and the like; and lower alkylene, forexample, ethylene, propylene, butylene, pentene, hexene, octene,norbomene, nonene, decene, and the like.

In addition, such alkyl groups may also contain various substituents inwhich one or more hydrogen atoms has been replaced by a functionalgroup. Functional groups include, but are not limited to hydroxyl,amino, carboxyl, sulfonic amide, ester, ether, phosphates, thiol, nitro,silane and halogen (fluorine, chlorine, bromine and iodine), to mentionbut a few.

As used herein, the term “substituted and unsubstituted carbocyclic”means cyclic carbon-containing compounds, including, but not limited tocyclopentyl, cyclohexyl, cycloheptyl, and the like. Such cyclic groupsmay also contain various substituents in which one or more hydrogenatoms has been replaced by a functional group. Such functional groupsinclude those described above, and lower alkyl groups having from 1-28carbon atoms. The cyclic groups of the invention may further comprise aheteroatom.

As mentioned above, R₁ and R₂ can also represent any combination ofalkyl, carbocyclic or aryl groups, for example, 1-cyclohexylpropyl,benzyl cyclohexylmethyl, 2-cyclohexylpropyl, 2,2-methylcyclohexylpropyl,2,2-methylphenylpropyl, and 2,2-methylphenylbutyl.

Non-grafted metallocene-catalyzed polymers useful in the presentinvention are commercially available under the trade name AFFINITY®polyolefin plastomers and ENGAGE® polyolefin elastomers commerciallyavailable from Dow Chemical Company and DuPont-Dow. Other commerciallyavailable metallocene-catalyzed polymers can be used, such as EXACT®,commercially available from Exxon and INSIGHT®, commercially availablefrom Dow. The EXACT® and INSIGHT® line of polymers also have novelrheological behavior in addition to their other properties as a resultof using a metallocene catalyst technology. Metallocene-catalyzedpolymers are also readily available from Sentinel Products Corporationof Hyannis, Mass., as foamed sheets for compression molding.

Monomers useful in the present invention include, but are not limitedto, olefinic monomers having, as a functional group, sulfonic acid,sulfonic acid derivatives, such as chlorosulfonic acid, vinyl ethers,vinyl esters, primary, secondary, and tertiary amines, mono-carboxylicacids, dicarboxylic acids, partially or fully ester-derivatizedmono-carboxylic and dicarboxylic acids, anhydrides of dicarboxylicacids, and cyclic imides of dicarboxylic acids.

In addition, metallocene-catalyzed polymers may also be functionalizedby sulfonation, carboxylation, or the addition of an amine or hydroxygroup. Metallocene-catalyzed polymers functionalized by sulfonation,carboxylation, or the addition of a hydroxy group may be converted toanionic ionomers by treatment with a base. Similarly,metallocene-catalyzed polymers functionalized by the addition of anamine may be converted to cationic ionomers by treatment with an alkylhalide, acid, or acid derivative.

The most preferred monomer is maleic anhydride, which, once attached tothe metallocene-catalyzed polymer by the post-polymerization reaction,may be further subjected to a reaction to form a graftedmetallocene-catalyzed polymer containing other pendant or functionalgroups. For example, reaction with water will convert the anhydride to adicarboxylic acid; reaction with ammonia, alkyl, or aromatic amine formsan amide; reaction with an alcohol results in the formation of an ester;and reaction with base results in the formation of an anionic ionomer.

The HNP's of the present invention may also be blended with single-siteand metallocene catalysts and polymers formed therefrom. As used herein,the term “single-site catalyst,” such as those disclosed in U.S. Pat.No. 6,150,462 which is incorporated herein by reference, refers to acatalyst that contains an ancillary ligand that influences the stearicand electronic characteristics of the polymerizing site in a manner thatprevents formation of secondary polymerizing species. The term“metallocene catalyst” refers to a single-site catalyst wherein theancillary ligands are comprising substituted or unsubstitutedcyclopentadienyl groups, and the term “non-metallocene catalyst” refersto a single-site catalyst other than a metallocene catalyst.

Non-metallocene single-site catalysts include, but are not limited to,the Brookhart catalyst, which has the following structure:

wherein M is nickel or palladium; R and R′ are independently hydrogen,hydrocarbyl, or substituted hydrocarbyl; Ar is (CF₃)₂C₆H₃, and X isalkyl, methyl, hydride, or halide; the McConville catalyst, which hasthe structure:

wherein M is titanium or zirconium. Iron (II) and cobalt (II) complexeswith 2,6-bis(imino) pyridyl ligands, which have the structure:

where M is the metal, and R is hydrogen, alkyl, or hydrocarbyl. Titaniumor zirconium complexes with pyrroles as ligands also serve assingle-site catalysts. These complexes have the structure:

where M is the metal atom; m and n are independently 1 to 4, andindicate the number of substituent groups attached to the aromaticrings; R_(m) and R_(n) are independently hydrogen or alkyl; and X ishalide or alkyl. Other examples include diamide complexes of nickel andpalladium, which have the structure:

where Ar is aromatic, M is the metal, and X is halide or alkyl.Boratabenzene complexes of the Group IV or V metals also function assingle-site catalysts. These complexes have the structure:

and

where B is boron and M is the metal atom.

As used herein, the term “single-site catalyzed polymer” refers to anypolymer, copolymer, or terpolymer, and, in particular, any polyolefinpolymerized using a single-site catalyst. The term “non-metallocenesingle-site catalyzed polymer” refers to any polymer, copolymer, orterpolymer, and, in particular, any polyolefin polymerized using asingle-site catalyst other than a metallocene-catalyst. The catalystsdiscussed above are examples of non-metallocene single-site catalysts.The term “metallocene catalyzed polymer” refers to any polymer,copolymer, or terpolymer, and, in particular, any polyolefin,polymerized using a metallocene catalyst.

As used herein, the term “single-site catalyzed polymer blend” refers toany blend of a single-site catalyzed polymer and any other type ofpolymer, preferably an ionomer, as well as any blend of a single-sitecatalyzed polymer with another single-site catalyzed polymer, including,but not limited to, a metallocene-catalyzed polymer.

The terms “grafted single-site catalyzed polymer” and “graftedsingle-site catalyzed polymer blend” refer to any single-site catalyzedpolymer or single-site catalyzed polymer blend in which the single-sitecatalyzed polymer has been subjected to a post-polymerization reactionto graft at least one functional group onto the single-site catalyzedpolymer. A “post-polymerization reaction” is any reaction that occursafter the formation of the polymer by a polymerization reaction.

The single-site catalyzed polymer, which may be grafted, may also beblended with polymers, such as non-grafted single-site catalyzedpolymers, grafted single-site catalyzed polymers, ionomers, andthermoplastic elastomers. Preferably, the single-site catalyzed polymeris blended with at least one ionomer of the preset invention.

Grafted single-site catalyzed polymers useful in the golf balls of theinvention may be obtained by subjecting a non-grafted single-sitecatalyzed polymer to a post-polymerization reaction to provide a graftedsingle-site catalyzed polymer with the desired pendant group or groups.Examples of single-site catalyzed polymers to which functional groupsmay be grafted for use in the invention include, but are not limited to,homopolymers of ethylene and propylene and copolymers of ethylene and asecond olefin, preferably, propylene, butene, pentene, hexene, heptene,octene, and norbomene. Monomers useful in the present invention include,but are not limited to olefinic monomers having as a functional groupsulfonic acid, sulfonic acid derivatives, such as chlorosulfonic acid,vinyl ethers, vinyl esters, primary, secondary, and tertiary amines,epoxies, isocyanates, mono-carboxylic acids, dicarboxylic acids,partially or fully ester derivatized mono-carboxylic and dicarboxylicacids, anhydrides of dicarboxylic acids, and cyclic imides ofdicarboxylic acids. Generally, this embodiment of the invention includesgolf balls having at least one layer comprising at least one graftedsingle-site catalyzed polymer or polymer blend, where the graftedsingle-site catalyzed polymer is produced by grafting a functional grouponto a single-site catalyzed polymer having the formula:

where R₁ is hydrogen, branched or straight chain alkyl such as methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, carbocyclic,aromatic or heterocyclic; R₂, R₃, R₅, and R₆ are hydrogen, lower alkylincluding C₁-C₅, carbocyclic, aromatic or heterocyclic; R₄ is H,C_(n)H_(2n+1), where n=1 to 18, and phenyl, in which from 0 to 5 Hwithin R₄ can be replaced by substituents such as COOH, SO₃H, NH₂, F,Cl, Br, I, OH, SH, epoxy, isocyanate, silicone, lower alkyl esters andlower alkyl ethers; also, R₃ and R₄ can be combined to form a bicyclicring; and x, y and z are the relative percentages of each co-monomer. Xcan range from about 1 to about 100 percent or more preferably from 1 to70 percent and most preferred, from about 1 to about 50 percent. Y canbe from about 99 to about 0 percent, preferably, from about 9 to about30 percent, or most preferably, about 9 to about 50 percent. Z can rangefrom about 0 to about 50 percent. One of ordinary skill in the art wouldalso understand that if an acid group is selected as a ligand in theabove structure that it too could be neutralized with the organic fattyacids described above.

The HNP's of the present invention may also be blended with highcrystalline acid copolymers and their ionomer derivatives (which may beneutralized with conventional metal cations or the organic fatty acidsand salts thereof) or a blend of a high crystalline acid copolymer andits ionomer derivatives and at least one additional material, preferablyan acid copolymer and its ionomer derivatives. As used herein, the term“high crystalline acid copolymer” is defined as a “product-by-process”in which an acid copolymer or its ionomer derivatives formed from aethylene/carboxylic acid copolymer comprising about 5 to about 35percent by weight acrylic or methacrylic acid, wherein the copolymer ispolymerized at a temperature of about 130° C. to 200° C., at pressuresgreater than about 20,000 psi preferably greater than about 25,000 psi,more pref. from about 25,000 psi to about 50,000 psi, wherein up toabout 70 percent, preferably 100 percent, of the acid groups areneutralized with a metal ion, organic fatty acids and salts thereof, ora mixture thereof. The copolymer can have a melt index (“MI”) of fromabout 20 to about 300 g/10 min, preferably about 20 to about 200 g/10min, and upon neutralization of the copolymer, the resulting acidcopolymer and its ionomer derivatives should have an MI of from about0.1 to about 30.0 g/10 min.

Suitable high crystalline acid copolymer and its ionomer derivativescompositions and methods for making them are disclosed in U.S. Pat. No.5,580,927, the disclosure of which is hereby incorporated by referencein its entirety.

The high crystalline acid copolymer or its ionomer derivatives employedin the present invention are preferably formed from a copolymercontaining about 5 to about 35 percent, more preferably from about 9 toabout 18, most preferably about 10 to about 13 percent, by weight ofacrylic acid, wherein up to about 75 percent, most preferably about 60percent, of the acid groups are neutralized with an organic fatty acid,salt thereof, or a metal ion, such as sodium, lithium, magnesium, orzinc ion.

Generally speaking, high crystalline acid copolymer and its ionomerderivatives are formed by polymerization of their base copolymers atlower temperatures, but at equivalent pressures to those used forforming a conventional acid copolymer and its ionomer derivatives.Conventional acid copolymers are typically polymerized at apolymerization temperature of from at least about 200° C. to about 270°C., preferably about 220° C., and at pressures of from about 23,000 toabout 30,000 psi. In comparison, the high crystalline acid copolymer andits ionomer derivatives employed in the present invention are producedfrom acid copolymers that are polymerized at a polymerizationtemperature of less than 200° C., and preferably from about 130° C. toabout 200° C., and at pressures from about 20,000 to about 50,000 psi.

The HNP's of the present invention may also be blended with cationicionomers, such as those disclosed in U.S. Pat. No. 6,193,619 which isincorporated herein by reference. In particular, cationic ionomers havea structure according to the formula:

or the formula:

wherein R₁-R₉ are organic moieties of linear or branched chain alkyl,carbocyclic, or aryl; and Z is the negatively charged conjugate ionproduced following alkylation and/or quaternization. The cationicpolymers may also be quarternized up to 100% by the organic fatty acidsdescribed above.

In addition, such alkyl group may also contain various substituents inwhich one or more hydrogen atoms has been replaced by a functionalgroup. Functional groups include but are not limited to hydroxyl, amino,carboxyl, amide, ester, ether, sulfonic, siloxane, siloxyl, silanes,sulfonyl, and halogen.

As used herein, substituted and unsubstituted carbocyclic groups of upto about 20 carbon atoms means cyclic carbon-containing compounds,including but not limited to cyclopentyl, cyclohexyl, cycloheptyl, andthe like. Such cyclic groups may also contain various substituents inwhich one or more hydrogen atoms has been replaced by a functionalgroup. Such functional groups include those described above, and loweralkyl groups as described above. The cyclic groups of the invention mayfurther comprise a heteroatom.

The HNP's of the present invention may also be blended with polyurethaneand polyurea ionomers which include anionic moieties or groups, such asthose disclosed in U.S. Pat. No. 6,207,784 which is incorporated hereinby reference. Typically, such groups are incorporated onto thediisocyanate or diisocyanate component of the polyurethane or polyureaionomers. The anionic group can also be attached to the polyol or aminecomponent of the polyurethane or polyurea, respectively. Preferably, theanionic group is based on a sulfonic, carboxylic or phosphoric acidgroup. Also, more than one type of anionic group can be incorporatedinto the polyurethane or polyurea. Examples of anionic polyurethaneionomers with anionic groups attached to the diisocyanate moiety canhave a chemical structure according to the following formula:

where A=R—Z⁻M^(+x); R is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; Z=SO₃ ⁻, CO₂ ⁻ or HPO₃ ⁻; M is a groupIA, IB, IIA, IIIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB or VIIIBmetal; x=1 to 5; B is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; and n=1 to 100. Preferably, M^(+x) is oneof the following: Li⁺, Na⁺, K⁺, Mg⁺², Zn⁺², Ca⁺², Mn⁺², Al⁺³, Ti^(+x),Zr^(+x), W^(+x) or Hf^(x).

Exemplary anionic polyurethane ionomers with anionic groups attached tothe polyol component of the polyurethane are characterized by the abovechemical structure where A is a straight chain or branched aliphaticgroup, a substituted straight chain or branched aliphatic group, or anaromatic or substituted aromatic group; B=R—Z⁻M^(+x); R is a straightchain or branched aliphatic group, a substituted straight chain orbranched aliphatic group, or an aromatic or substituted aromatic group;Z=SO₃ ⁻, CO₂ ⁻ or HPO₃ ⁻; M is a group IA, IB, IIA, IIB, IIIA, IIIB,IVA, IVB, VA, VB, VIA, VIB, VIIB or VIIIB metal; x=1 to 5; and n=1 to100. Preferably, M^(+x) is one of the following: Li⁺, Na⁺, K⁺, Mg⁺²,Zn⁺², Ca⁺², Mn⁺², Al⁺³, Ti^(+x), Zr^(+x), W^(+x) or Hf^(+x).

Examples of suitable anionic polyurea ionomers with anionic groupsattached to the diisocyanate component have a chemical structureaccording to the following chemical structure:

where A=R—Z⁻M^(+x); R is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; Z=SO₃ ⁻, CO₂ ⁻ or HPO₃ ⁻; M is a groupIA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB or VIIIBmetal; x=1 to 5; and B is a straight chain or branched aliphatic group,a substituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group. Preferably, M^(+x) is one of thefollowing: Li⁺, Na⁺, K⁺, Mg⁺², Zn⁺², Ca⁺², Mn⁺², Al⁺³, Ti^(+x), Zr^(+x),W^(+x), or Hf^(+x).

Suitable anionic polyurea ionomers with anionic groups attached to theamine component of the polyurea are characterized by the above chemicalstructure where A is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; B=R—Z—M^(+x); R is a straight chain orbranched aliphatic group, a substituted straight chain or branchedaliphatic group, or an aromatic or substituted aromatic group; Z=SO₃ ⁻,CO₂ ⁻, or HPO₃ ⁻; M is a group IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB,VA, VB, VIA, VIB, VIIB or VIIIB metal; and x=1 to 5. Preferably, M^(+x)is one of the following: Li⁺, Na⁺, K⁺, Mg⁺², Zn⁺², Ca⁺², Mn⁺², Al⁺³,Ti^(+x), Zr^(+x), W^(+x), or Hf^(+x). The anionic polyurethane andpolyurea ionomers may also be neutralized up to 100% by the organicfatty acids described above.

The anionic polymers useful in the present invention, such as thosedisclosed in U.S. Pat. No. 6,221,960 which is incorporated herein byreference, include any homopolymer, copolymer or terpolymer havingneutralizable hydroxyl and/or dealkylable ether groups, and in which atleast a portion of the neutralizable or dealkylable groups areneutralized or dealkylated with a metal ion.

As used herein “neutralizable” or “dealkylable” groups refer to ahydroxyl or ether group pendent from the polymer chain and capable ofbeing neutralized or dealkylated by a metal ion, preferably a metal ionbase. These neutralized polymers have improved properties critical togolf ball performance, such as resiliency, impact strength and toughnessand abrasion resistance. Suitable metal bases are ionic compoundscomprising a metal cation and a basic anion. Examples of such basesinclude hydroxides, carbonates, acetates, oxides, sulfides, and thelike.

The particular base to be used depends upon the nature of the hydroxylor ether compound to be neutralized or dealkylated, and is readilydetermined by one skilled in the art. Preferred anionic bases includehydroxides, carbonates, oxides and acetates.

The metal ion can be any metal ion which forms an ionic compound withthe anionic base. The metal is not particularly limited, and includesalkali metals, preferably lithium, sodium or potassium; alkaline earthmetals, preferably magnesium or calcium; transition metals, preferablytitanium, zirconium, or zinc; and Group III and IV metals. The metal ioncan have a +1 to +5 charge. Most preferably, the metal is lithium,sodium, potassium, zinc, magnesium, titanium, tungsten, or calcium, andthe base is hydroxide, carbonate or acetate.

The anionic polymers useful in the present invention include those whichcontain neutralizable hydroxyl and/or dealkylable ether groups.Exemplary polymers include ethylene vinyl alcohol copolymers, polyvinylalcohol, polyvinyl acetate, poly(p-hydroxymethylene styrene), andp-methoxy styrene, to name but a few. It will be apparent to one skilledin the art that many such polymers exist and thus can be used in thecompositions of the invention. In general, the anionic polymer can bedescribed by the chemical structure:

where R₁ is OH, OC(O)R_(a), O—M^(+V), (CH₂)_(n)R_(b), (CHR₂)_(n)R_(b),or aryl, wherein n is at least 1, R_(a) is a lower alkyl, M is a metalion, V is an integer from 1 to 5, R_(b) is OH, OC(O)R_(a), O—M^(+V), andR_(Z) is a lower alkyl or aryl, and R₂, R₃ and R₄ are each independentlyhydrogen, straight-chain or branched-chain lower alkyl. R₂, R₃ and R₄may also be similarly substituted. Preferably n is from 1 to 12, morepreferably 1 to 4.

The term “substituted,” as used herein, means one or more hydrogen atomshas been replaced by a functional group. Functional groups include, butare not limited to, hydroxyl, amino, carboxyl, sulfonic, amide, ether,ether, phosphates, thiol, nitro, silane, and halogen, as well as manyothers which are quite familiar to those of ordinary skill in this art.

The terms “alkyl” or “lower alkyl,” as used herein, includes a group offrom about 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms.

In the anionic polymers useful in the present invention, at least aportion of the neutralizable or dealkylable groups of R₁ are neutralizedor dealkylated by an organic fatty acid, a salt thereof, a metal base,or a mixture thereof to form the corresponding anionic moiety. Theportion of the neutralizable or dealkylable groups which are neutralizedor dealkylated can be between about 1 to about 100 weight percent,preferably between about 50 to about 100 weight percent, more preferablybefore about 90 to about 100.

Neutralization or dealkylation may be performed by melting the polymerfirst, then adding a metal ion in an extruder. The degree ofneutralization or dealkylation is controlled by varying the amount ofmetal ion added. Any method of neutralization or dealkylation availableto those of ordinary skill in the art may also be suitably employed.

In one embodiment, the anionic polymer is repeating units any one of thethree homopolymer units in the chemical structure above. In a preferredembodiment, R₂, R₃ and R₄ are hydrogen, and R₁ is hydroxyl, i.e., theanionic polymer is a polyvinyl alcohol homopolymer in which a portion ofthe hydroxyl groups have been neutralized with a metal base. In anotherpreferred embodiment, R₂, R₃ and R₄ are hydrogen, R₁ is OC(O)R_(a), andR_(a) is methyl, i.e., the anionic polymer is a polyvinyl acetatehomopolymer in which a portion of the methyl ether groups have beendealkylated with a metal ion.

The anionic polymer can also be a copolymer of two different repeatingunits having different substituents, or a terpolymer of three differentrepeating units described in the above formula. In this embodiment, thepolymer can be a random copolymer, an alternating copolymer, or a blockcopolymer, where the term “copolymer” includes terpolymers.

In another embodiment, the anionic polymer is a copolymer, wherein R₅,R₆, R₇ and R₈ are each independently selected from the group definedabove for R₂. The first unit of the copolymer can comprise from about 1to 99 percent weight percent of the polymer, preferably from about 5 to50 weight percent, and the second unit of the copolymer can comprisefrom about 99 to 1 weight percent, preferably from about 95 to 50 weightpercent. In one preferred embodiment, the anionic polymer is a random,alternating or block copolymer of units (Ia) and (Ib) wherein R₁ ishydroxyl, and each of the remaining R groups is hydrogen, i.e., thepolymer is a copolymer of ethylene and vinyl alcohol. In anotherpreferred embodiment, the anionic polymer is a random, alternating orblock copolymer of units (Ia) and (Ib) wherein R₁ is OC(O)R₅, where R₅is methyl, and each of the remaining R groups is hydrogen, i.e., thepolymer is a copolymer of ethylene and vinyl acetate.

In another embodiment, the anionic polymer is an anionic polymer havingneutralizable hydroxyl and/or dealkylable ether groups of as in theabove chemical structure wherein R₁₋₉ and R_(b) and R_(z) are as definedabove; R₁₀₋₁₁ are each independently selected from the group as definedabove for R₂; and R₁₂ is OH or OC(O)R₁₃, where R₁₃ is a lower alkyl;wherein x, y and z indicate relative weight percent of the differentunits. X can be from about 99 to about 50 weight percent of the polymer,y can be from about 1 to about 50 weight percent of the polymer, and zranges from about 0 to about 50 weight percent of the polymer. At leasta portion of the neutralizable groups R₁ are neutralized. When theamount of z is greater than zero, a portion of the groups R₁₀ can alsobe fully or partially neutralized, as desired.

In particular, the anionic polymers and blends thereof can comprisecompatible blends of anionic polymers and ionomers, such as the ionomersdescribed above, and ethylene acrylic methacrylic acid ionomers, andtheir terpolymers, sold commercially under the trade names SURLYN® andIOTEK® by DuPont and Exxon respectively. The anionic polymer blendsuseful in the golf balls of the invention can also include otherpolymers, such as polyvinylalcohol, copolymers of ethylene and vinylalcohol, poly(ethylethylene), poly(heptylethylene),poly(hexyldecylethylene), poly(isopentylethylene), poly(butyl acrylate),acrylate), poly(2-ethylbutyl acrylate), poly(heptyl acrylate),poly(2-methylbutyl acrylate), poly(3-methylbutyl acrylate),poly(N-octadecylacrylamide), poly(octadecyl methacrylate),poly(butoxyethylene), poly(methoxyethylene), poly(pentyloxyethylene),poly(1,1-dichloroethylene), poly(4-[(2-butoxyethoxy)methyl]styrene),poly[oxy(ethoxymethyl)ethylene], poly(oxyethylethylene),poly(oxytetramethylene), poly(oxytrimethylene), poly(silanes) andpoly(silazanes), polyamides, polycarbonates, polyesters, styrene blockcopolymers, polyetheramides, polyurethanes, main-chain heterocyclicpolymers and poly(furan tetracarboxylic acid diimides), as well as theclasses of polymers to which they belong.

The anionic polymer compositions of the present invention typically havea flexural modulus of from about 500 psi to about 300,000 psi,preferably from about 2000 to about 200,000 psi. The anionic polymercompositions typically have a material hardness of at least about 15Shore A, preferably between about 30 Shore A and 80 Shore D, morepreferably between about 50 Shore A and 60 Shore D. The loss tangent, ordissipation factor, is a ratio of the loss modulus over the dynamicshear storage modulus, and is typically less than about 1, preferablyless than about 0.01, and more preferably less than about 0.001 for theanionic polymer compositions measured at about 23° C. The specificgravity is typically greater than about 0.7, preferably greater thanabout 1, for the anionic polymer compositions. The dynamic shear storagemodulus, or storage modulus, of the anionic polymer compositions atabout 23° C. is typically at least about 10,000 dyn/cm².

The base rubber typically includes natural or synthetic rubbers. Apreferred base rubber is 1,4-polybutadiene having a cis-structure of atleast 40%. More preferably, the base rubber compriseshigh-Mooney-viscosity rubber. If desired, the polybutadiene can also bemixed with other elastomers known in the art such as natural rubber,polyisoprene rubber and/or styrene-butadiene rubber in order to modifythe properties of the core.

The crosslinking agent includes a metal salt of an unsaturated fattyacid such as a zinc salt or a magnesium salt of an unsaturated fattyacid having 3 to 8 carbon atoms such as acrylic or methacrylic acid.Suitable cross linking agents include metal salt diacrylates,dimethacrylates and monomethacrylates wherein the metal is magnesium,calcium, zinc, aluminum, sodium, lithium or nickel. The crosslinkingagent is present in an amount from about 15 to about 30 parts perhundred of the rubber, preferably in an amount from about 19 to about 25parts per hundred of the rubber and most preferably having about 20 to24 parts crosslinking agent per hundred of rubber. The core compositionsof the present invention may also include at least one organic orinorganic cis-trans catalyst to convert a portion of the cis-isomer ofpolybutadiene to the trans-isomer, as desired.

The initiator agent can be any known polymerization initiator whichdecomposes during the cure cycle. Suitable initiators include peroxidecompounds such as dicumyl peroxide, 1,1-di-(t-butylperoxy)3,3,5-trimethyl cyclohexane, a-a bis-(t-butylperoxy) diisopropylbenzene,2,5-dimethyl-2,5 di-(t-butylperoxy) hexane or di-t-butyl peroxide andmixtures thereof.

Fillers, any compound or composition that can be used to vary thedensity and other properties of the core, typically include materialssuch as tungsten, zinc oxide, barium sulfate, silica, calcium carbonate,zinc carbonate, metals, metal oxides and salts, regrind (recycled corematerial typically ground to about 30 mesh particle),high-Mooney-viscosity rubber regrind, and the like.

The golf ball center of the present invention may also comprise avariety of constructions. For example, the center may comprise a singlelayer or a plurality of layers. The center may also comprise a formed ofa tensioned elastomeric material. In another embodiment of the presentinvention, golf ball comprises a solid center surrounded by at least oneadditional solid outer core layer. The “dual” core is surrounded by a“double” cover comprising an inner cover layer and an outer cover layer.

At least one of the outer core layers is formed of a resilientrubber-based component comprising a high-Mooney-viscosity rubber, and acrosslinking agent present in an amount from about 20 to about 40 partsper hundred, from about 30 to about 38 parts per hundred, and mostpreferably about 37 parts per hundred. It should be understood that theterm “parts per hundred” is with reference to the rubber by weight.

When the golf ball of the present invention includes an intermediatelayer, such as an outer core layer or an inner cover layer, any or allof these layer(s) may comprise thermoplastic and thermosetting material,but preferably the intermediate layer(s), if present, comprise anysuitable material, such as ionic copolymers of ethylene and anunsaturated monocarboxylic acid which are available under the trademarkSURLYN® of E.I. DuPont de Nemours & Co., of Wilmington, Del., or IOTEK®or ESCOR® of Exxon. These are copolymers or terpolymers of ethylene andmethacrylic acid or acrylic acid partially neutralized with salts ofzinc, sodium, lithium, magnesium, potassium, calcium, manganese, nickelor the like, in which the salts are the reaction product of an olefinhaving from 2 to 8 carbon atoms and an unsaturated monocarboxylic acidhaving 3 to 8 carbon atoms. The carboxylic acid groups of the copolymermay be totally or partially neutralized and might include methacrylic,crotonic, maleic, fumaric or itaconic acid.

This golf ball can likewise include one or more homopolymeric orcopolymeric inner cover materials, such as:

-   -   (1) Vinyl resins, such as those formed by the polymerization of        vinyl chloride, or by the copolymerization of vinyl chloride        with vinyl acetate, acrylic esters or vinylidene chloride;    -   (2) Polyolefins, such as polyethylene, polypropylene,        polybutylene and copolymers such as ethylene methylacrylate,        ethylene ethylacrylate, ethylene vinyl acetate, ethylene        methacrylic or ethylene acrylic acid or propylene acrylic acid        and copolymers and homopolymers produced using a single-site        catalyst or a metallocene catalyst;    -   (3) Polyurethanes, such as those prepared from polyols and        diisocyanates or polyisocyanates, in particular PPDI-based        thermoplastic polyurethanes, and those disclosed in U.S. Pat.        No. 5,334,673;    -   (4) Polyureas, such as those disclosed in U.S. Pat. No.        5,484,870;    -   (5) Polyamides, such as poly(hexamethylene adipamide) and others        prepared from diamines and dibasic acids, as well as those from        amino acids such as poly(caprolactam), and blends of polyamides        with SURLYN®, polyethylene, ethylene copolymers,        ethylene-propylene-non-conjugated diene terpolymer, and the        like;    -   (6) Acrylic resins and blends of these resins with poly vinyl        chloride, elastomers, and the like;    -   (7) Thermoplastics, such as urethane; olefinic thermoplastic        rubbers, such as blends of polyolefins with        ethylene-propylene-non-conjugated diene terpolymer; block        copolymers of styrene and butadiene, isoprene or        ethylene-butylene rubber; or copoly(ether-amide), such as        PEBAX®, sold by ELF Atochem of Philadelphia, Pa.;    -   (8) Polyphenylene oxide resins or blends of polyphenylene oxide        with high impact polystyrene as sold under the trademark NORYL®        by General Electric Company of Pittsfield, Mass.;    -   (9) Thermoplastic polyesters, such as polyethylene        terephthalate, polybutylene terephthalate, polyethylene        terephthalate/glycol modified, poly(trimethylene terepthalate),        and elastomers sold under the trademarks HYTREL® by E.I. DuPont        de Nemours & Co. of Wilmington, Del., and LOMOD® by General        Electric Company of Pittsfield, Mass.;    -   (10) Blends and alloys, including polycarbonate with        acrylonitrile butadiene styrene, polybutylene terephthalate,        polyethylene terephthalate, styrene maleic anhydride,        polyethylene, elastomers, and the like, and polyvinyl chloride        with acrylonitrile butadiene styrene or ethylene vinyl acetate        or other elastomers; and    -   (11) Blends of thermoplastic rubbers with polyethylene,        propylene, polyacetal, nylon, polyesters, cellulose esters, and        the like.

Preferably, the inner cover includes polymers, such as ethylene,propylene, butene-1 or hexane-1 based homopolymers or copolymersincluding functional monomers, such as acrylic and methacrylic acid andfully or partially neutralized ionomer resins and their blends, methylacrylate, methyl methacrylate homopolymers and copolymers, imidized,amino group containing polymers, polycarbonate, reinforced polyamides,polyphenylene oxide, high impact polystyrene, polyether ketone,polysulfone, poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers, and blends thereof. Suitable cover compositions also includea polyether or polyester thermoplastic urethane, a thermosetpolyurethane, a low modulus ionomer, such as acid-containing ethylenecopolymer ionomers, including E/X/Y terpolymers where E is ethylene, Xis an acrylate or methacrylate-based softening comonomer present inabout 0 to 50 weight percent and Y is acrylic or methacrylic acidpresent in about 5 to 35 weight percent. More preferably, in a low spinrate embodiment designed for maximum distance, the acrylic ormethacrylic acid is present in about 16 to 35 weight percent, making theionomer a high modulus ionomer. In a higher spin embodiment, the innercover layer includes an ionomer where an acid is present in about 10 to15 weight percent and includes a softening comonomer. Additionally,high-density polyethylene (“HDPE”), low-density polyethylene (“LDPE”),LLDPE, and homo- and co-polymers of polyolefin are suitable for avariety of golf ball layers.

In one embodiment, the outer cover preferably includes a polyurethanecomposition comprising the reaction product of at least onepolyisocyanate, polyol, and at least one curing agent. Anypolyisocyanate available to one of ordinary skill in the art is suitablefor use according to the invention. Exemplary polyisocyanates include,but are not limited to, 4,4′-diphenylmethane diisocyanate (“MDI”);polymeric MDI; carbodiimide-modified liquid MDI;4,4′-dicyclohexylmethane diisocyanate (“H₁₂MDI”); p-phenylenediisocyanate (“PPDI”); m-phenylene diisocyanate (“MPDI”); toluenediisocyanate (“TDI”); 3,3′-dimethyl-4,4′-biphenylene diisocyanate(“TODI”); isophoronediisocyanate (“IPDI”); hexamethylene diisocyanate(“HDI”); naphthalene diisocyanate (“NDI”); xylene diisocyanate (“XDI”);p-tetramethylxylene diisocyanate (“p-TMXDI”); m-tetramethylxylenediisocyanate (“m-TMXDI”); ethylene diisocyanate;propylene-1,2-diisocyanate; tetramethylene-1,4-diisocyanate; cyclohexyldiisocyanate; 1,6-hexamethylene-diisocyanate (“HDI”);dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; methylcyclohexylene diisocyanate; triisocyanate of HDI; triisocyanate of2,4,4-trimethyl-1,6-hexane diisocyanate (“TMDI”); tetracenediisocyanate; napthalene diisocyanate; anthracene diisocyanate;isocyanurate of toluene diisocyanate; uretdione of hexamethylenediisocyanate; and mixtures thereof. Polyisocyanates are known to thoseof ordinary skill in the art as having more than one isocyanate group,e.g., di-isocyanate, tri-isocyanate, and tetra-isocyanate. Preferably,the polyisocyanate includes MDI, PPDI, TDI, or a mixture thereof, andmore preferably, the polyisocyanate includes MDI. It should beunderstood that, as used herein, the term “MDI” includes4,4′-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modifiedliquid MDI, and mixtures thereof and, additionally, that thediisocyanate employed may be “low free monomer,” understood by one ofordinary skill in the art to have lower levels of “free” monomerisocyanate groups, typically less than about 0.1% free monomer groups.Examples of “low free monomer” diisocyanates include, but are notlimited to Low Free Monomer MDI, Low Free Monomer TDI, and Low FreeMonomer PPDI.

The at least one polyisocyanate should have less than about 14%unreacted NCO groups. Preferably, the at least one polyisocyanate has nogreater than about 7.5% NCO, and more preferably, less than about 7.0%.

Any polyol available to one of ordinary skill in the art is suitable foruse according to the invention. Exemplary polyols include, but are notlimited to, polyether polyols, hydroxy-terminated polybutadiene(including partially/fully hydrogenated derivatives), polyester polyols,polycaprolactone polyols, and polycarbonate polyols. In one preferredembodiment, the polyol includes polyether polyol. Examples include, butare not limited to, polytetramethylene ether glycol (“PTMEG”),polyethylene propylene glycol, polyoxypropylene glycol, and mixturesthereof. The hydrocarbon chain can have saturated or unsaturated bondsand substituted or unsubstituted aromatic and cyclic groups. Preferably,the polyol of the present invention includes PTMEG.

In another embodiment, polyester polyols are included in thepolyurethane material of the invention. Suitable polyester polyolsinclude, but are not limited to, polyethylene adipate glycol;polybutylene adipate glycol; polyethylene propylene adipate glycol;o-phthalate-1,6-hexanediol; poly(hexamethylene adipate) glycol; andmixtures thereof. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups.

In another embodiment, polycaprolactone polyols are included in thematerials of the invention. Suitable polycaprolactone polyols include,but are not limited to, 1,6-hexanediol-initiated polycaprolactone,diethylene glycol initiated polycaprolactone, trimethylol propaneinitiated polycaprolactone, neopentyl glycol initiated polycaprolactone,1,4-butanediol-initiated polycaprolactone, and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds, orsubstituted or unsubstituted aromatic and cyclic groups.

In yet another embodiment, the polycarbonate polyols are included in thepolyurethane material of the invention. Suitable polycarbonates include,but are not limited to, polyphthalate carbonate and poly(hexamethylenecarbonate) glycol. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups. In one embodiment, the molecular weight of the polyol is fromabout 200 to about 4000.

Polyamine curatives are also suitable for use in the polyurethanecomposition of the invention and have been found to improve cut, shear,and impact resistance of the resultant balls. Preferred polyaminecuratives include, but are not limited to,3,5-dimethylthio-2,4-toluenediamine and isomers thereof;3,5-diethyltoluene-2,4-diamine and isomers thereof, such as3,5-diethyltoluene-2,6-diamine;4,4′-bis-(sec-butylamino)-diphenylmethane;1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline);4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”);polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenylmethane; p,p′-methylene dianiline (“MDA”); m-phenylenediamine (“MPDA”);4,4′-methylene-bis-(2-chloroaniline) (“MOCA”);4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”);4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”);4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane;2,2′,3,3′-tetrachloro diamino diphenylmethane; trimethylene glycoldi-p-aminobenzoate; and mixtures thereof. Preferably, the curing agentof the present invention includes 3,5-dimethylthio-2,4-toluenediamineand isomers thereof, such as ETHACURE 300, commercially available fromAlbermarle Corporation of Baton Rouge, La. Suitable polyamine curatives,which include both primary and secondary amines, preferably havemolecular weights ranging from about 64 to about 2000.

At least one of a diol, triol, tetraol, or hydroxy-terminated curativesmay be added to the aforementioned polyurethane composition. Suitablediol, triol, and tetraol groups include ethylene glycol; diethyleneglycol; polyethylene glycol; propylene glycol; polypropylene glycol;lower molecular weight polytetramethylene ether glycol;1,3-bis(2-hydroxyethoxy) benzene; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy} benzene;1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol;resorcinol-di-(β-hydroxyethyl) ether; hydroquinone-di-(β-hydroxyethyl)ether; and mixtures thereof. Preferred hydroxy-terminated curativesinclude 1,3-bis(2-hydroxyethoxy) benzene; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy] benzene; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}benzene;1,4-butanediol, and mixtures thereof. Preferably, the hydroxy-terminatedcuratives have molecular weights ranging from about 48 to 2000. Itshould be understood that molecular weight, as used herein, is theabsolute weight average molecular weight and would be understood as suchby one of ordinary skill in the art.

Both the hydroxy-terminated and amine curatives can include one or moresaturated, unsaturated, aromatic, and cyclic groups. Additionally, thehydroxy-terminated and amine curatives can include one or more halogengroups. The polyurethane composition can be formed with a blend ormixture of curing agents. If desired, however, the polyurethanecomposition may be formed with a single curing agent.

In a preferred embodiment of the present invention, saturatedpolyurethanes used to form cover layers, preferably the outer coverlayer, and may be selected from among both castable thermoset andthermoplastic polyurethanes.

In this embodiment, the saturated polyurethanes of the present inventionare substantially free of aromatic groups or moieties. Saturatedpolyurethanes suitable for use in the invention are a product of areaction between at least one polyurethane prepolymer and at least onesaturated curing agent. The polyurethane prepolymer is a product formedby a reaction between at least one saturated polyol and at least onesaturated diisocyanate. As is well known in the art, a catalyst may beemployed to promote the reaction between the curing agent and theisocyanate and polyol.

Saturated diisocyanates which can be used include, without limitation,ethylene diisocyanate; propylene-1,2-diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (“HDI”);2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; dicyclohexylmethanediisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; isophoronediisocyanate (“IPDI”); methyl cyclohexylene diisocyanate ; triisocyanateof HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane diisocyanate(“TMDI”). The most preferred saturated diisocyanates are4,4′-dicyclohexylmethane diisocyanate (“HMDI”) and isophoronediisocyanate (“IPDI”).

Saturated polyols which are appropriate for use in this inventioninclude without limitation polyether polyols such as polytetramethyleneether glycol and poly(oxypropylene) glycol. Suitable saturated polyesterpolyols include polyethylene adipate glycol, polyethylene propyleneadipate glycol, polybutylene adipate glycol, polycarbonate polyol andethylene oxide-capped polyoxypropylene diols. Saturated polycaprolactonepolyols which are useful in the invention include diethyleneglycol-initiated polycaprolactone, 1,4-butanediol-initiatedpolycaprolactone, 1,6-hexanediol-initiated polycaprolactone; trimethylolpropane-initiated polycaprolactone, neopentyl glycol initiatedpolycaprolactone, and polytetramethylene ether glycol-initiatedpolycaprolactone. The most preferred saturated polyols arepolytetramethylene ether glycol and PTMEG-initiated polycaprolactone.

Suitable saturated curatives include 1,4-butanediol, ethylene glycol,diethylene glycol, polytetramethylene ether glycol, propylene glycol;trimethanolpropane; tetra-(2-hydroxypropyl)-ethylenediamine; isomers andmixtures of isomers of cyclohexyldimethylol, isomers and mixtures ofisomers of cyclohexane bis(methylamine); triisopropanolamine; ethylenediamine; diethylene triamine; triethylene tetramine; tetraethylenepentamine; 4,4′-dicyclohexylmethane diamine;2,2,4-trimethyl-1,6-hexanediamine; 2,4,4-trimethyl-1,6-hexanediamine;diethyleneglycol di-(aminopropyl)ether;4,4′-bis-(sec-butylamino)-dicyclohexylmethane;1,2-bis-(sec-butylamino)cyclohexane; 1,4-bis-(sec-butylamino)cyclohexane; isophorone diamine; hexamethylene diamine; propylenediamine; 1-methyl-2,4-cyclohexyl diamine; 1-methyl-2,6-cyclohexyldiamine; 1,3-diaminopropane; dimethylamino propylamine; diethylaminopropylamine; imido-bis-propylamine; isomers and mixtures of isomers ofdiaminocyclohexane; monoethanolamine; diethanolamine; triethanolamine;monoisopropanolamine; and diisopropanolamine. The most preferredsaturated curatives are 1,4-butanediol, 1,4-cyclohexyldimethylol and4,4′-bis-(sec-butylamino)-dicyclohexylmethane. The compositions of theinvention may also be polyurea-based, which are distinctly differentfrom polyurethane compositions, but also result in desirable aerodynamicand aesthetic characteristics when used in golf ball components. Thepolyurea-based compositions are preferably saturated in nature.

Without being bound to any particular theory, it is now believed thatsubstitution of the long chain polyol segment in the polyurethaneprepolymer with a long chain polyamine oligomer soft segment to form apolyurea prepolymer, improves shear, cut, and resiliency, as well asadhesion to other components. Thus, the polyurea compositions of thisinvention may be formed from the reaction product of an isocyanate andpolyamine prepolymer crosslinked with a curing agent. For example,polyurea-based compositions of the invention may be prepared from atleast one isocyanate, at least one polyether amine, and at least onediol curing agent or at least one diamine curing agent.

Any polyamine available to one of ordinary skill in the art is suitablefor use in the polyurea prepolymer. Polyether amines are particularlysuitable for use in the prepolymer. As used herein, “polyether amines”refer to at least polyoxyalkyleneamines containing primary amino groupsattached to the terminus of a polyether backbone. Due to the rapidreaction of isocyanate and amine, and the insolubility of many ureaproducts, however, the selection of diamines and polyether amines islimited to those allowing the successful formation of the polyureaprepolymers. In one embodiment, the polyether backbone is based ontetramethylene, propylene, ethylene, trimethylolpropane, glycerin, andmixtures thereof.

Suitable polyether amines include, but are not limited to,methyldiethanolamine; polyoxyalkylenediamines such as,polytetramethylene ether diamines, polyoxypropylenetriamine, andpolyoxypropylene diamines; poly(ethylene oxide capped oxypropylene)ether diamines; propylene oxide-based triamines;triethyleneglycoldiamines; trimethylolpropane-based triamines;glycerin-based triamines; and mixtures thereof. In one embodiment, thepolyether amine used to form the prepolymer is JEFFAMINE® D2000(manufactured by Huntsman Chemical Co. of Austin, Tex.).

The molecular weight of the polyether amine for use in the polyureaprepolymer may range from about 100 to about 5000. As used herein, theterm “about” is used in connection with one or more numbers or numericalranges, should be understood to refer to all such numbers, including allnumbers in a range. In one embodiment, the polyether amine molecularweight is about 200 or greater, preferably about 230 or greater. Inanother embodiment, the molecular weight of the polyether amine is about4000 or less. In yet another embodiment, the molecular weight of thepolyether amine is about 600 or greater. In still another embodiment,the molecular weight of the polyether amine is about 3000 or less. Inyet another embodiment, the molecular weight of the polyether amine isbetween about 1000 and about 3000, and more preferably is between about1500 to about 2500. Because lower molecular weight polyether amines maybe prone to forming solid polyureas, a higher molecular weight oligomer,such as Jeffamine D2000, is preferred.

In one embodiment, the polyether amine has the generic structure:

wherein the repeating unit x has a value ranging from about 1 to about70. Even more preferably, the repeating unit may be from about 5 toabout 50, and even more preferably is from about 12 to about 35.

In another embodiment, the polyether amine has the generic structure:

wherein the repeating units x and z have combined values from about 3.6to about 8 and the repeating unit y has a value ranging from about 9 toabout 50, and wherein R is —(CH₂)_(a)—, where “a” may be a repeatingunit ranging from about 1 to about 10.

In yet another embodiment, the polyether amine has the genericstructure:H₂N—(R)—O—(R)—O—(R)—NH₂wherein R is —(CH₂)_(a)—, and “a” may be a repeating unit ranging fromabout 1 to about 10.

As briefly discussed above, some amines may be unsuitable for reactionwith the isocyanate because of the rapid reaction between the twocomponents. In particular, shorter chain amines are fast reacting. Inone embodiment, however, a hindered secondary diamine may be suitablefor use in the prepolymer. Without being bound to any particular theory,it is believed that an amine with a high level of stearic hindrance,e.g., a tertiary butyl group on the nitrogen atom, has a slower reactionrate than an amine with no hindrance or a low level of hindrance. Forexample, 4,4′-bis-(sec-butylamino)-dicyclohexylmethane (CLEARLINK® 1000)may be suitable for use in combination with an isocyanate to form thepolyurea prepolymer.

Any isocyanate available to one of ordinary skill in the art is suitablefor use in the polyurea prepolymer. Isocyanates for use with the presentinvention include aliphatic, cycloaliphatic, araliphatic, aromatic, anyderivatives thereof, and combinations of these compounds having two ormore isocyanate (NCO) groups per molecule. The isocyanates may beorganic polyisocyanate-terminated prepolymers. The isocyanate-containingreactable component may also include any isocyanate-functional monomer,dimer, trimer, or multimeric adduct thereof, prepolymer,quasi-prepolymer, or mixtures thereof. Isocyanate-functional compoundsmay include monoisocyanates or polyisocyanates that include anyisocyanate functionality of two or more.

Suitable isocyanate-containing components include diisocyanates havingthe generic structure: O═C═N—R—N═C═O, where R is preferably a cyclic,aromatic, or linear or branched hydrocarbon moiety containing from about1 to about 20 carbon atoms. The diisocyanate may also contain one ormore cyclic groups or one or more phenyl groups. When multiple cyclic oraromatic groups are present, linear and/or branched hydrocarbonscontaining from about 1 to about 10 carbon atoms can be present asspacers between the cyclic or aromatic groups. In some cases, the cyclicor aromatic group(s) may be substituted at the 2-, 3-, and/or4-positions, or at the ortho-, meta-, and/or para-positions,respectively. Substituted groups may include, but are not limited to,halogens, primary, secondary, or tertiary hydrocarbon groups, or amixture thereof.

Examples of diisocyanates that can be used with the present inventioninclude, but are not limited to, substituted and isomeric mixturesincluding 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate (MDI);3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI); toluene diisocyanate(TDI); polymeric MDI; carbodiimide-modified liquid 4,4′-diphenylmethanediisocyanate; para-phenylene diisocyanate (PPDI); meta-phenylenediisocyanate (MPDI); triphenyl methane-4,4′- and triphenylmethane-4,4′-triisocyanate; naphthylene-1,5-diisocyanate; 2,4′-, 4,4′-,and 2,2-biphenyl diisocyanate; polyphenyl polymethylene polyisocyanate(PMDI); mixtures of MDI and PMDI; mixtures of PMDI and TDI; ethylenediisocyanate; propylene-1,2-diisocyanate;tetramethylene-1,2-diisocyanate; tetramethylene-1,3-diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (HDI);octamethylene diisocyanate; decamethylene diisocyanate;2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethanediisocyanate (H₁₂MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; 1,2-, 1,3-, and 1,4-phenylenediisocyanate; aromatic aliphatic isocyanate, such as 1,2-, 1,3-, and1,4-xylene diisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, isocyanurateof isophorone diisocyanate, and mixtures thereof; dimerized uredione ofany polyisocyanate, such as uretdione of toluene diisocyanate, uretdioneof hexamethylene diisocyanate, and mixtures thereof; modifiedpolyisocyanate derived from the above isocyanates and polyisocyanates;and mixtures thereof.

Examples of saturated diisocyanates that can be used with the presentinvention include, but are not limited to, ethylene diisocyanate;propylene-1,2-diisocyanate; tetramethylene diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (HDI);octamethylene diisocyanate; decamethylene diisocyanate;2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethanediisocyanate (H₁₂MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; and mixtures thereof. Aromaticaliphatic isocyanates may also be used to form light stable materials.Examples of such isocyanates include 1,2-, 1,3-, and 1,4-xylenediisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, isocyanurateof isophorone diisocyanate, and mixtures thereof; dimerized uredione ofany polyisocyanate, such as uretdione of toluene diisocyanate, uretdioneof hexamethylene diisocyanate, and mixtures thereof; modifiedpolyisocyanate derived from the above isocyanates and polyisocyanates;and mixtures thereof. In addition, the aromatic aliphatic isocyanatesmay be mixed with any of the saturated isocyanates listed above for thepurposes of this invention.

The number of unreacted NCO groups in the polyurea prepolymer ofisocyanate and polyether amine may be varied to control such factors asthe speed of the reaction, the resultant hardness of the composition,and the like. For instance, the number of unreacted NCO groups in thepolyurea prepolymer of isocyanate and polyether amine may be less thanabout 14 percent. In one embodiment, the polyurea prepolymer has fromabout 5 percent to about 11 percent unreacted NCO groups, and even morepreferably has from about 6 to about 9.5 percent unreacted NCO groups.In one embodiment, the percentage of unreacted NCO groups is about 3percent to about 9 percent. Alternatively, the percentage of unreactedNCO groups in the polyurea prepolymer may be about 7.5 percent or less,and more preferably, about 7 percent or less. In another embodiment, theunreacted NCO content is from about 2.5 percent to about 7.5 percent,and more preferably from about 4 percent to about 6.5 percent.

When formed, polyurea prepolymers may contain about 10 percent to about20 percent by weight of the prepolymer of free isocyanate monomer. Thus,in one embodiment, the polyurea prepolymer may be stripped of the freeisocyanate monomer. For example, after stripping, the prepolymer maycontain about 1 percent or less free isocyanate monomer. In anotherembodiment, the prepolymer contains about 0.5 percent by weight or lessof free isocyanate monomer.

The polyether amine may be blended with additional polyols to formulatecopolymers that are reacted with excess isocyanate to form the polyureaprepolymer. In one embodiment, less than about 30 percent polyol byweight of the copolymer is blended with the saturated polyether amine.In another embodiment, less than about 20 percent polyol by weight ofthe copolymer, preferably less than about 15 percent by weight of thecopolymer, is blended with the polyether amine. The polyols listed abovewith respect to the polyurethane prepolymer, e.g., polyether polyols,polycaprolactone polyols, polyester polyols, polycarbonate polyols,hydrocarbon polyols, other polyols, and mixtures thereof, are alsosuitable for blending with the polyether amine. The molecular weight ofthese polymers may be from about 200 to about 4000, but also may be fromabout 1000 to about 3000, and more preferably are from about 1500 toabout 2500.

The polyurea composition can be formed by crosslinking the polyureaprepolymer with a single curing agent or a blend of curing agents. Thecuring agent of the invention is preferably an amine-terminated curingagent, more preferably a secondary diamine curing agent so that thecomposition contains only urea linkages. In one embodiment, theamine-terminated curing agent may have a molecular weight of about 64 orgreater. In another embodiment, the molecular weight of the amine-curingagent is about 2000 or less. As discussed above, certainamine-terminated curing agents may be modified with a compatibleamine-terminated freezing point depressing agent or mixture ofcompatible freezing point depressing agents.

Suitable amine-terminated curing agents include, but are not limited to,ethylene diamine; hexamethylene diamine; 1-methyl-2,6-cyclohexyldiamine; tetrahydroxypropylene ethylene diamine; 2,2,4- and2,4,4-trimethyl-1,6-hexanediamine;4,4′-bis-(sec-butylamino)-dicyclohexylmethane;1,4-bis-(sec-butylamino)-cyclohexane;1,2-bis-(sec-butylamino)-cyclohexane; derivatives of4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 4,4′-dicyclohexylmethanediamine; 1,4-cyclohexane-bis-(methylamine);1,3-cyclohexane-bis-(methylamine); diethylene glycol di-(aminopropyl)ether; 2-methylpentamethylene-diamine; diaminocyclohexane; diethylenetriamine; triethylene tetramine; tetraethylene pentamine; propylenediamine; 1,3-diaminopropane; dimethylamino propylamine; diethylaminopropylamine; dipropylene triamine; imido-bis-propylamine;monoethanolamine, diethanolamine; triethanolamine; monoisopropanolamine,diisopropanolamine; isophoronediamine;4,4′-methylenebis-(2-chloroaniline);3,5;dimethylthio-2,4-toluenediamine;3,5-dimethylthio-2,6-toluenediamine; 3,5-diethylthio-2,4-toluenediamine;3,5;diethylthio-2,6-toluenediamine;4,4′-bis-(sec-butylamino)-diphenylmethane and derivatives thereof;1,4-bis-(sec-butylamino)-benzene; 1,2-bis-(sec-butylamino)-benzene;N,N′-dialkylamino-diphenylmethane; N,N,N′,N′-tetrakis (2-hydroxypropyl)ethylene diamine; trimethyleneglycol-di-p-aminobenzoate;polytetramethyleneoxide-di-p-aminobenzoate;4,4′-methylenebis-(3-chloro-2,6-diethyleneaniline);4,4′-methylenebis-(2,6-diethylaniline); meta-phenylenediamine;paraphenylenediamine; and mixtures thereof. In one embodiment, theamine-terminated curing agent is4,4′-bis-(sec-butylamino)-dicyclohexylmethane.

Suitable saturated amine-terminated curing agents include, but are notlimited to, ethylene diamine; hexamethylene diamine;1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene diamine;2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine;4,4′-bis-(sec-butylamino)-dicyclohexylmethane;1,4-bis-(sec-butylamino)-cyclohexane;1,2-bis-(sec-butylamino)-cyclohexane; derivatives of4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 4,4′-dicyclohexylmethanediamine; 4,4′-methylenebis-(2,6-diethylaminocyclohexane;1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine);diethylene glycol di-(aminopropyl) ether;2-methylpentamethylene-diamine; diaminocyclohexane; diethylene triamine;triethylene tetramine; tetraethylene pentamine; propylene diamine;1,3-diaminopropane; dimethylamino propylamine; diethylamino propylamine;imido-bis-propylamine; monoethanolamine, diethanolamine;triethanolamine; monoisopropanolamine, diisopropanolamine;isophoronediamine; triisopropanolamine; and mixtures thereof. Inaddition, any of the polyether amines listed above may be used as curingagents to react with the polyurea prepolymers.

Suitable catalysts include, but are not limited to bismuth catalyst,oleic acid, triethylenediamine (DABCO®-33LV), di-butyltin dilaurate(DABCO®-T12) and acetic acid. The most preferred catalyst is di-butyltindilaurate (DABCO®-T12). DABCO® materials are manufactured by AirProducts and Chemicals, Inc.

Thermoplastic materials may be blended with other thermoplasticmaterials, but thermosetting materials are difficult if not impossibleto blend homogeneously after the thermosetting materials are formed.Preferably, the saturated polyurethane comprises from about 1% to about100%, more preferably from about 10% to about 75% of the covercomposition and/or the intermediate layer composition. About 90% toabout 10%, more preferably from about 90% to about 25% of the coverand/or the intermediate layer composition is comprised of one or moreother polymers and/or other materials as described below. Such polymersinclude, but are not limited to polyurethane/polyurea ionomers,polyurethanes or polyureas, epoxy resins, polyethylenes, polyamides andpolyesters, polycarbonates and polyacrylin. Unless otherwise statedherein, all percentages are given in percent by weight of the totalcomposition of the golf ball layer in question.

Polyurethane prepolymers are produced by combining at least one polyol,such as a polyether, polycaprolactone, polycarbonate or a polyester, andat least one isocyanate. Thermosetting polyurethanes are obtained bycuring at least one polyurethane prepolymer with a curing agent selectedfrom a polyamine, triol or tetraol. Thermoplastic polyurethanes areobtained by curing at least one polyurethane prepolymer with a diolcuring agent. The choice of the curatives is critical because someurethane elastomers that are cured with a diol and/or blends of diols donot produce urethane elastomers with the impact resistance required in agolf ball cover. Blending the polyamine curatives with diol curedurethane elastomeric formulations leads to the production of thermoseturethanes with improved impact and cut resistance.

Thermoplastic polyurethanes may be blended with suitable materials toproduce a thermoplastic end product. Examples of such additionalmaterials may include ionomers such as the SURLYN®, ESCOR® and IOTEK®copolymers described above.

Other suitable materials which may be combined with the saturatedpolyurethanes in forming the cover and/or intermediate layer(s) of thegolf balls of the invention include ionic or non-ionic polyurethanes andpolyureas, epoxy resins, polyethylenes, polyamides and polyesters. Forexample, the cover and/or intermediate layer may be formed from a blendof at least one saturated polyurethane and thermoplastic or thermosetionic and non-ionic urethanes and polyurethanes, cationic urethaneionomers and urethane epoxies, ionic and non-ionic polyureas and blendsthereof Examples of suitable urethane ionomers are disclosed in U.S.Pat. No. 5,692,974 entitled “Golf Ball Covers”, the disclosure of whichis hereby incorporated by reference in its entirety. Other examples ofsuitable polyurethanes are described in U.S. Pat. No. 5,334,673.Examples of appropriate polyureas are discussed in U.S. Pat. No.5,484,870 and examples of suitable polyurethanes cured with epoxy groupcontaining curing agents are disclosed in U.S. Pat. No. 5,908,358, thedisclosures of which are hereby incorporated herein by reference intheir entirety.

A variety of conventional components can be added to the covercompositions of the present invention. These include, but are notlimited to, white pigment such as TiO₂, ZnO, optical brighteners,surfactants, processing aids, foaming agents, density-controllingfillers, UV stabilizers and light stabilizers. Saturated polyurethanesare resistant to discoloration. However, they are not immune todeterioration in their mechanical properties upon weathering. Additionof UV absorbers and light stabilizers therefore helps to maintain thetensile strength and elongation of the saturated polyurethaneelastomers. Suitable UV absorbers and light stabilizers include TINUVIN®328, TINUVIN® 213, TINUVIN 765, TINUVIN® 770 and TINUVIN® 622. Thepreferred UV absorber is TINUVIN® 328, and the preferred lightstabilizer is TINUVIN® 765. TINUVIN® products are available fromCiba-Geigy. Dyes, as well as optical brighteners and fluorescentpigments may also be included in the golf ball covers produced withpolymers formed according to the present invention. Such additionalingredients may be added in any amounts that will achieve their desiredpurpose.

Any method known to one of ordinary skill in the art may be used topolyurethanes of the present invention. One commonly employed method,known in the art as a one-shot method, involves concurrent mixing of thepolyisocyanate, polyol, and curing agent. This method results in amixture that is inhomogenous (more random) and affords the manufacturerless control over the molecular structure of the resultant composition.A preferred method of mixing is known as a prepolymer method. In thismethod, the polyisocyanate and the polyol are mixed separately prior toaddition of the curing agent. This method affords a more homogeneousmixture resulting in a more consistent polymer composition. Othermethods suitable for forming the layers of the present invention includereaction injection molding (“RIM”), liquid injection molding (“LIM”),and pre-reacting the components to form an injection moldablethermoplastic polyurethane and then injection molding, all of which areknown to one of ordinary skill in the art.

Additional components which can be added to the polyurethane compositioninclude UV stabilizers and other dyes, as well as optical brightenersand fluorescent pigments and dyes. Such additional ingredients may beadded in any amounts that will achieve their desired purpose. It hasbeen found by the present invention that the use of a castable, reactivematerial, which is applied in a fluid form, makes it possible to obtainvery thin outer cover layers on golf balls. Specifically, it has beenfound that castable, reactive liquids, which react to form a urethaneelastomer material, provide desirable very thin outer cover layers.

The castable, reactive liquid employed to form the urethane elastomermaterial can be applied over the core using a variety of applicationtechniques such as spraying, dipping, spin coating, or flow coatingmethods which are well known in the art. An example of a suitablecoating technique is that which is disclosed in U.S. Pat. No. 5,733,428,the disclosure of which is hereby incorporated by reference in itsentirety.

The outer cover is preferably formed around the inner cover by mixingand introducing the material in the mold halves. It is important thatthe viscosity be measured over time, so that the subsequent steps offilling each mold half, introducing the core into one half and closingthe mold can be properly timed for accomplishing centering of the corecover halves fusion and achieving overall uniformity. Suitable viscosityrange of the curing urethane mix for introducing cores into the moldhalves is determined to be approximately between about 2,000 cP andabout 30,000 cP, with the preferred range of about 8,000 cP to about15,000 cP.

To start the cover formation, mixing of the prepolymer and curative isaccomplished in motorized mixer including mixing head by feeding throughlines metered amounts of curative and prepolymer. Top preheated moldhalves are filled and placed in fixture units using centering pinsmoving into holes in each mold. At a later time, a bottom mold half or aseries of bottom mold halves have similar mixture amounts introducedinto the cavity. After the reacting materials have resided in top moldhalves for about 40 to about 80 seconds, a core is lowered at acontrolled speed into the gelling reacting mixture.

A ball cup holds the ball core through reduced pressure (or partialvacuum). Upon location of the coated core in the halves of the moldafter gelling for about 40 to about 80 seconds, the vacuum is releasedallowing core to be released. The mold halves, with core and solidifiedcover half thereon, are removed from the centering fixture unit,inverted and mated with other mold halves which, at an appropriate timeearlier, have had a selected quantity of reacting polyurethaneprepolymer and curing agent introduced therein to commence gelling.

Similarly, U.S. Pat. No. 5,006,297 to Brown et al. and U.S. Pat. No.5,334,673 to Wu both also disclose suitable molding techniques which maybe utilized to apply the castable reactive liquids employed in thepresent invention. Further, U.S. Pat. Nos. 6,180,040 and 6,180,722disclose methods of preparing dual core golf balls. The disclosures ofthese patents are hereby incorporated by reference in their entirety.However, the method of the invention is not limited to the use of thesetechniques.

Depending on the desired properties, balls prepared according to theinvention can exhibit substantially the same or higher resilience, orcoefficient of restitution (“COR”), with a decrease in compression ormodulus, compared to balls of conventional construction. Additionally,balls prepared according to the invention can also exhibit substantiallyhigher resilience, or COR, without an increase in compression, comparedto balls of conventional construction. Another measure of thisresilience is the “loss tangent,” or tan δ, which is obtained whenmeasuring the dynamic stiffness of an object. Loss tangent andterminology relating to such dynamic properties is typically describedaccording to ASTM D4092-90. Thus, a lower loss tangent indicates ahigher resiliency, thereby indicating a higher rebound capacity. Lowloss tangent indicates that most of the energy imparted to a golf ballfrom the club is converted to dynamic energy, i.e., launch velocity andresulting longer distance. The rigidity or compressive stiffness of agolf ball may be measured, for example, by the dynamic stiffness. Ahigher dynamic stiffness indicates a higher compressive stiffness. Toproduce golf balls having a desirable compressive stiffness, the dynamicstiffness of the crosslinked reaction product material should be lessthan about 50,000 N/m at −50° C. Preferably, the dynamic stiffnessshould be between about 10,000 and 40,000 N/m at −50° C., morepreferably, the dynamic stiffness should be between about 20,000 and30,000 N/m at −50° C.

The molding process and composition of golf ball portions typicallyresults in a gradient of material properties. Methods employed in theprior art generally exploit hardness to quantify these gradients.Hardness is a qualitative measure of static modulus and does notrepresent the modulus of the material at the deformation ratesassociated with golf ball use, i.e., impact by a club. As is well knownto one skilled in the art of polymer science, the time-temperaturesuperposition principle may be used to emulate alternative deformationrates. For golf ball portions including polybutadiene, a 1-Hzoscillation at temperatures between 0° C. and −50° C. are believed to bequalitatively equivalent to golf ball impact rates. Therefore,measurement of loss tangent and dynamic stiffness at 0° C. to −50° C.may be used to accurately anticipate golf ball performance, preferablyat temperatures between about −20° C. and −50° C.

In another embodiment of the present invention, a golf ball of thepresent invention is substantially spherical and has a cover with aplurality of dimples formed on the outer surface thereof.

U.S. application Ser. No. 10/230,015, now U.S. Publication No.2003/0114565, and U.S. application Ser. No. 10/108,793, now U.S.Publication No. 2003/0050373, which are incorporated by reference hereinin their entirety, discuss soft, high resilient ionomers, which arepreferably from neutralizing the acid copolymer(s) of at least one E/X/Ycopolymer, where E is ethylene, X is the α,β-ethylenically unsaturatedcarboxylic acid, and Y is a softening co-monomer. X is preferablypresent in 2-30 (preferably 4-20, most preferably 5-15) wt. % of thepolymer, and Y is preferably present in 17-40 (preferably 20-40, andmore preferably 24-35) wt. % of the polymer. Preferably, the melt index(MI) of the base resin is at least 20, or at least 40, more preferably,at least 75 and most preferably at least 150. Particular soft, resilientionomers included in this invention are partially neutralizedethylene/(meth) acrylic acid /butyl (meth) acrylate copolymers having anMI and level of neutralization that results in a melt processiblepolymer that has useful physical properties. The copolymers are at leastpartially neutralized. Preferably at least 40, or, more preferably atleast 55, even more preferably about 70, and most preferably about 80 ofthe acid moiety of the acid copolymer is neutralized by one or morealkali metal, transition metal, or alkaline earth metal cations. Cationsuseful in making the ionomers of this invention comprise lithium,sodium, potassium, magnesium, calcium, barium, or zinc, or a combinationof such cations.

The invention also relates to a “modified” soft, resilient thermoplasticionomer that comprises a melt blend of (a) the acid copolymers or themelt processible ionomers made therefrom as described above and (b) oneor more organic acid(s) or salt(s) thereof, wherein greater than 80%,preferably greater than 90% of all the acid of (a) and of (b) isneutralized. Preferably, 100% of all the acid of (a) and (b) isneutralized by a cation source. Preferably, an amount of cation sourcein excess of the amount required to neutralize 100% of the acid in (a)and (b) is used to neutralize the acid in (a) and (b). Blends with fattyacids or fatty acid salts are preferred.

The organic acids or salts thereof are added in an amount sufficient toenhance the resilience of the copolymer. Preferably, the organic acidsor salts thereof are added in an amount sufficient to substantiallyremove remaining ethylene crystallinity of the copolymer.

Preferably, the organic acids or salts are added in an amount of atleast about 5% (weight basis) of the total amount of copolymer andorganic acid(s). More preferably, the organic acids or salts thereof areadded in an amount of at least about 15%, even more preferably at leastabout 20%. Preferably, the organic acid(s) are added in an amount up toabout 50% (weight basis) based on the total amount of copolymer andorganic acid. More preferably, the organic acids or salts thereof areadded in an amount of up to about 40%, more preferably, up to about 35%.The non-volatile, non-migratory organic acids preferably are one or morealiphatic, mono-functional organic acids or salts thereof as describedbelow, particularly one or more aliphatic, mono-functional, saturated orunsaturated organic acids having less than 36 carbon atoms or salts ofthe organic acids, preferably stearic acid or oleic acid. Fatty acids orfatty acid salts are most preferred.

Processes for fatty acid (salt) modifications are known in the art.Particularly, the modified highly-neutralized soft, resilient acidcopolymer ionomers of this invention can be produced by:

-   -   (a) melt-blending (1) ethylene, α,β-ethylenically unsaturated        C₃₋₈ carboxylic acid copolymer(s) or melt-processible ionomer(s)        thereof that have their crystallinity disrupted by addition of a        softening monomer or other means with (2) sufficient        non-volatile, non-migratory organic acids to substantially        enhance the resilience and to disrupt (preferably remove) the        remaining ethylene crystallinity, and then concurrently or        subsequently    -   (b) adding a sufficient amount of a cation source to increase        the level of neutralization of all the acid moieties (including        those in the acid copolymer and in the organic acid if the        non-volatile, non-migratory organic acid is an organic acid) to        the desired level.

The weight ratio of X to Y in the composition is at least about 1:20.Preferably, the weight ratio of X to Y is at least about 1:15, morepreferably, at least about 1:10. Furthermore, the weight ratio of X to Yis up to about 1:1.67, more preferably up to about 1:2. Most preferably,the weight ratio of X to Y in the composition is up to about 1:2.2.

The acid copolymers used in the present invention to make the ionomersare preferably ‘direct’ acid copolymers (containing high levels ofsoftening monomers). As noted above, the copolymers are at leastpartially neutralized, preferably at least about 40% of X in thecomposition is neutralized. More preferably, at least about 55% of X isneutralized. Even more preferably, at least about 70, and mostpreferably, at least about 80% of X is neutralized. In the event thatthe copolymer is highly neutralized (e.g., to at least 45%, preferably50%, 55%, 70%, or 80%, of acid moiety), the MI of the acid copolymershould be sufficiently high so that the resulting neutralized resin hasa measurable MI in accord with ASTM D-1238, condition E, at 190° C.,using a 2160 gram weight. Preferably this resulting MI will be at least0.1, preferably at least 0.5, and more preferably 1.0 or greater.Preferably, for highly neutralized acid copolymer, the MI of the acidcopolymer base resin is at least 20, or at least 40, at least 75, andmore preferably at least 150.

The acid copolymers preferably comprise alpha olefin, particularlyethylene, C₃₋₈. α,β-ethylenically unsaturated carboxylic acid,particularly acrylic and methacrylic acid, and softening monomers,selected from alkyl acrylate, and alkyl methacrylate, wherein the alkylgroups have from 1-8 carbon atoms, copolymers. By “softening,” it ismeant that the crystallinity is disrupted (the polymer is made lesscrystalline). While the alpha olefin can be a C₂-C₄ alpha olefin,ethylene is most preferred for use in the present invention.Accordingly, it is described and illustrated herein in terms of ethyleneas the alpha olefin.

The acid copolymers, when the alpha olefin is ethylene, can be describedas E/X/Y copolymers where E is ethylene, X is the α,β-ethylenicallyunsaturated carboxylic acid, and Y is a softening comonomer; X ispreferably present in 2-30 (preferably 4-20, most preferably 5-15) wt. %of the polymer, and Y is preferably present in 17-40 (preferably 20-40,most preferably 24-35) wt. % of the polymer.

The ethylene-acid copolymers with high levels of acid (X) are difficultto prepare in continuous polymerizers because of monomer-polymer phaseseparation. This difficulty can be avoided however by use of “co-solventtechnology” as described in U.S. Pat. No. 5,028,674, or by employingsomewhat higher pressures than those which copolymers with lower acidcan be prepared.

Specific acid-copolymers include ethylene/(meth) acrylic acid/n-butyl(meth) acrylate, ethylene/(meth) acrylic acid/iso-butyl (meth) acrylate,ethylene/(meth) acrylic acid/methyl (meth) acrylate, and ethylene/(meth)acrylic acid/ethyl (meth) acrylate terpolymers.

The organic acids employed are aliphatic, mono-functional (saturated,unsaturated, or multi-unsaturated) organic acids, particularly thosehaving fewer than 36 carbon atoms. Also salts of these organic acids maybe employed. Fatty acids or fatty acid salts are preferred. The saltsmay be any of a wide variety, particularly including the barium,lithium, sodium, zinc, bismuth, potassium, strontium, magnesium orcalcium salts of the organic acids. Particular organic acids useful inthe present invention include caproic acid, caprylic acid, capric acid,lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, andlinoleic acid.

The optional filler component is chosen to impart additional density toblends of the previously described components, the selection beingdependent upon the different parts (e.g., cover, mantle, core, center,intermediate layers in a multilayered core or ball) and the type of golfball desired (e.g., one-piece, two-piece, three-piece or multiple-pieceball), as will be more fully detailed below.

Generally, the filler will be inorganic having a density greater thanabout 4 g/cm³, preferably greater than 5 g/cm³, and will be present inamounts between 0 to about 60 wt. % based on the total weight of thecomposition. Examples of useful fillers include zinc oxide, bariumsulfate, lead silicate and tungsten carbide, as well as the otherwell-known fillers used in golf balls. It is preferred that the fillermaterials be non-reactive or almost non-reactive and not stiffen orraise the compression nor reduce the coefficient of restitutionsignificantly.

Additional optional additives useful in the practice of the subjectinvention include acid copolymer wax (e.g., Allied wax AC 143 believedto be an ethylene/16-18% acrylic acid copolymer with a number averagemolecular weight of 2,040), which assist in preventing reaction betweenthe filler materials (e.g., ZnO) and the acid moiety in the ethylenecopolymer. Other optional additives include TiO₂, which is used as awhitening agent; optical brighteners; surfactants; processing aids; etc.

Ionomers may be blended with conventional ionomeric copolymers (di-,ter-, etc.), using well-known techniques, to manipulate productproperties as desired. The blends would still exhibit lower hardness andhigher resilience when compared with blends based on conventionalionomers.

Also, ionomers can be blended with non-ionic thermoplastic resins tomanipulate product properties. The non-ionic thermoplastic resins would,by way of non-limiting illustrative examples, include thermoplasticelastomers, such as polyurethane, poly-ether-ester, poly-amide-ether,polyether-urea, PEBAX® (a family of block copolymers based onpolyether-block-amide, commercially supplied by Atochem),styrene-butadiene-styrene (SBS) block copolymers,styrene(ethylene-butylene)-styrene block copolymers, etc., poly amide(oligomeric and polymeric), polyesters, polyolefins including PE, PP,E/P copolymers, etc., ethylene copolymers with various comonomers, suchas vinyl acetate, (meth)acrylates, (meth)acrylic acid,epoxy-functionalized monomer, CO, etc., functionalized polymers withmaleic anhydride grafting, epoxidization etc., elastomers, such as EPDM,metallocene catalyzed PE and copolymer, ground up powders of thethermoset elastomers, etc. Such thermoplastic blends comprise about 1%to about 99% by weight of a first thermoplastic and about 99% to about1% by weight of a second thermoplastic.

Additionally, the compositions of U.S. application Ser. No. 10/269,341,now U.S. Publication No. 2003/0130434, and U.S. Pat. No. 6,653,382, bothof which are incorporated herein in their entirety, discuss compositionshaving high COR when formed into solid spheres.

The thermoplastic composition of this invention comprises a polymerwhich, when formed into a sphere that is 1.50 to 1.54 inches indiameter, has a coefficient of restitution (COR) when measured by firingthe sphere at an initial velocity of 125 feet/second against a steelplate positioned 3 feet from the point where initial velocity andrebound velocity are determined and by dividing the rebound velocityfrom the plate by the initial velocity and an Atti compression of nomore than 100.

The thermoplastic composition of this invention preferably comprises (a)aliphatic, mono-functional organic acid(s) having fewer than 36 carbonatoms; and (b) ethylene, C₃ to C₈ α,β-ethylenically unsaturatedcarboxylic acid copolymer(s) and ionomer(s) thereof, wherein greaterthan 90%, preferably near 100%, and more preferably 100% of all the acidof (a) and (b) are neutralized.

The thermoplastic composition preferably comprises melt-processible,highly-neutralized (greater than 90%, preferably near 100%, and morepreferably 100%) polymer of (1) ethylene, C₃ to C₈ α,β-ethylenicallyunsaturated carboxylic acid copolymers that have their crystallinitydisrupted by addition of a softening monomer or other means such as highacid levels, and (2) non-volatile, non-migratory agents such as organicacids (or salts) selected for their ability to substantially or totallysuppress any remaining ethylene crystallinity. Agents other than organicacids (or salts) may be used.

It has been found that, by modifying an acid copolymer or ionomer with asufficient amount of specific organic acids (or salts thereof); it ispossible to highly neutralize the acid copolymer without losingprocessibility or properties such as elongation and toughness. Theorganic acids employed in the present invention are aliphatic,mono-functional, saturated or unsaturated organic acids, particularlythose having fewer than 36 carbon atoms, and particularly those that arenon-volatile and non-migratory and exhibit ionic array plasticizing andethylene crystallinity suppression properties.

With the addition of sufficient organic acid, greater than 90%, nearly100%, and preferably 100% of the acid moieties in the acid copolymerfrom which the ionomer is made can be neutralized without losing theprocessibility and properties of elongation and toughness.

The melt-processible, highly-neutralized acid copolymer ionomer can beproduced by the following:

-   -   (a) melt-blending (1) ethylene α,β-ethylenically unsaturated        C₃₋₈ carboxylic acid copolymer(s) or melt-processible ionomer(s)        thereof (ionomers that are not neutralized to the level that        they have become intractable, that is not melt-processible)        with (1) one or more aliphatic, mono-functional, saturated or        unsaturated organic acids having fewer than 36 carbon atoms or        salts of the organic acids, and then concurrently or        subsequently    -   (b) adding a sufficient amount of a cation source to increase        the level of neutralization all the acid moieties (including        those in the acid copolymer and in the organic acid) to greater        than 90%, preferably near 100%, more preferably to 100%.

Preferably, highly-neutralized thermoplastics of the invention can bemade by:

-   -   (a) melt-blending (1) ethylene, α,β-ethylenically unsaturated        C₃₋₈ carboxylic acid copolymer(s) or melt-processible ionomer(s)        thereof that have their crystallinity disrupted by addition of a        softening monomer or other means with (2) sufficient        non-volatile, non-migratory agents to substantially remove the        remaining ethylene crystallinity, and then concurrently or        subsequently    -   (b) adding a sufficient amount of a cation source to increase        the level of neutralization all the acid moieties (including        those in the acid copolymer and in the organic acid if the        non-volatile, non-migratory agent is an organic acid) to greater        than 90%, preferably near 100%, more preferably to 100%.

The acid copolymers used in the present invention to make the ionomersare preferably ‘direct’ acid copolymers. They are preferably alphaolefin, particularly ethylene, C₃₋₈ α,β-ethylenically unsaturatedcarboxylic acid, particularly acrylic and methacrylic acid, copolymers.They may optionally contain a third softening monomer. By “softening,”it is meant that the crystallinity is disrupted (the polymer is madeless crystalline). Suitable “softening” comonomers are monomers selectedfrom alkyl acrylate, and alkyl methacrylate, wherein the alkyl groupshave from 1-8 carbon atoms.

The acid copolymers, when the alpha olefin is ethylene, can be describedas E/X/Y copolymers where E is ethylene, X is the α,β-ethylenicallyunsaturated carboxylic acid, and Y is a softening comonomer. X ispreferably present in 3-30 (preferably 4-25, most preferably 5-20) wt. %of the polymer, and Y is preferably present in 0-30 (alternatively 3-25or 10-23) wt. % of the polymer.

Spheres were prepared using fully neutralized ionomers A and B.

TABLE I Cation (% Sample Resin Type (%) Acid Type (%) neut*) M.I. (g/10min) 1A A(60) Oleic (40) Mg (100) 1.0 2B A(60) Oleic (40) Mg (105)* 0.93C B(60) Oleic (40) Mg (100) 0.9 4D B(60) Oleic (40) Mg (105)* 0.9 5EB(60) Stearic (40) Mg (100) 0.85 A—76.9% ethylene, 14.8% normal butylacrylate, 8.3% acrylic acid B—75% ethylene, 14.9% normal butyl acrylate,10.1% acrylic acid *indicates that cation was sufficient to neutralize105% of all the acid in the resin and the organic acid.

These compositions were molded into 1.53-inch spheres for which data ispresented in the following table.

TABLE II Sample Atti Compression COR @ 125 ft/s 1A 75 0.826 2B 75 0.8263C 78 0.837 4D 76 0.837 5E 97 0.807

Further testing of commercially available highly neutralized polymersHNP1 and HNP2 had the following properties.

TABLE III Material Properties HNP1 HNP2 Specific Gravity (g/cm³) 0.9660.974 Melt Flow, 190° C., 10-kg load 0.65 1.0 Shore D Flex Bar (40 hr)47.0 46.0 Shore D Flex Bar (2 week) 51.0 48.0 Flex Modulus, psi (40 hr)25,800 16,100 Flex Modulus, psi (2 week) 39,900 21,000 DSC Melting Point(° C.) 61.0 61/101 Moisture (ppm) 1500 4500 Weight % Mg 2.65 2.96

TABLE IV Solid Sphere Data HNP1a/HNP2a Material HNP1 HNP2 HNP2a HNP1a(50:50 blend) Spec. Grav. 0.954 0.959 1.153 1.146 1.148 (g/cm³) FillerNone None Tungsten Tungsten Tungsten Compression 107 83 86 62 72 COR0.827 0.853 0.844 0.806 0.822 Shore D 51 47 49 42 45 Shore C 79 72 75These materials are exemplary examples of the preferred center and/orcore layer compositions of the present invention. They may also be usedas a cover layer herein.

The golf ball components of the present invention, in particular thecore (center and/or outer core layers) may be formed from a co-polymerof ethylene and an α,β-unsaturated carboxylic acid. In anotherembodiment, they may be formed from a terpolymer of ethylene, anα,β-unsaturated carboxylic acid, and an n-alkyl acrylate. Preferably,the α,β-unsaturated carboxylic acid is acrylic acid or methacrylic acid.In a preferred embodiment, the n-alkyl acrylate is n-butyl acrylate.Further, in a preferred form, the co- or ter-polymer comprises a levelof fatty acid salt greater than 5 phr of the base resin. The preferredfatty acid salt is magnesium oleate or magnesium stearate.

It is highly preferred that the carboxylic acid in the intermediatelayer is 100% neutralized with metal ions. The metal ions used toneutralize the carboxylic acid may be any metal ion known in the art.Preferably, the metal ions comprise magnesium ions. If the material usedin the intermediate layer is not 100% neutralized, the resultantresilience properties such as COR and initial velocity may not besufficient to produce the improved initial velocity and distanceproperties of the present invention.

The golf ball components can comprise various levels of the threecomponents of the co- or terpolymer as follows: from about 60 to about90% ethylene, from about 8 to about 20% by weight of the α,β-unsaturatedcarboxylic acid, and from 0% to about 25% of the n-alkyl acrylate. Theco- or terpolymer may also contain an amount of a fatty acid salt. Thefatty acid salt preferably comprises magnesium oleate. These materialsare commercially available from DuPont, under the tradename DuPont HPF®.

In one embodiment, the center and/or core layers (or other intermediatelayers) comprises a copolymer of about 81% by weight ethylene and about19% by weight acrylic acid, wherein 100% of the carboxylic acid groupsare neutralized with magnesium ions. The copolymer also contains atleast 5 phr of magnesium oleate. Material suitable for use as this layeris available from DuPont under the tradename DuPont HPF SEP 1313-4®.

In a second preferred embodiment, the core and/or core layers (or otherintermediate layers) comprise a copolymer of about 85% by weightethylene and about 15% by weight acrylic acid, wherein 100% of the acidgroups are neutralized with magnesium ions. The copolymer also containsat least 5 phr of magnesium oleate. Material suitable for use as thislayer is available from DuPont under the tradename DuPont HPF SEP1313-3®.

In a third preferred embodiment, the core and/or core layers (or otherintermediate layers) comprise a copolymer of about 88% by weightethylene and about 12% by weight acrylic acid, wherein 100% of the acidgroups are neutralized with magnesium ions. The copolymer also containsat least 5 phr of magnesium oleate. Material suitable for use as thislayer is available from DuPont under the tradenane DuPont HPF AD1027®.

In a further preferred embodiment, the core and/or core layers (or otherintermediate layers) are adjusted to a target specific gravity to enablethe ball to be balanced. For a 1.68-inch diameter golf ball having aball weight of about 1.61 oz, the target specific gravity is about1.125. It will be appreciated by one of ordinary skill in the art thatthe target specific gravity will vary based upon the size and weight ofthe golf ball. The specific gravity is adjusted to the desired targetthrough the use of inorganic fillers. Preferred fillers used forcompounding the inner layer to the desired specific gravity include, butare not limited to, tungsten, zinc oxide, barium sulfate and titaniumdioxide. Other suitable fillers, in particular nano or hybrid materials,include those described in U.S. Pat. No. 6,793,592 and U.S. applicationSer. No. 10/037,987, which are incorporated herein, in their entirety,by reference thereto.

Some preferred golf ball layers formed from the above compositions weremolded onto a golf ball center using DuPont HPF RX-85®, Dupont HPF SEP1313-3®, or DuPont HPF SEP 1313-4®. 1) DuPont HPF RX-85®, a copolymer ofabout 88% ethylene and about 12% acrylic acid, wherein 100% of the acidgroups are neutralized with magnesium ions. Further, the copolymercontains a fixed amount of magnesium oleate. This material wascompounded to a specific gravity of about 1.125 using tungsten. TheShore D hardness of this material (as measured on the curved surface ofthe inner cover layer) was about 58 to about 60. 2) DuPont HPF SEP1313-3®, a copolymer of about 85% ethylene and about 15% acrylic acid,wherein 100% of the acid groups are neutralized with magnesium ions.Further, the copolymer contains a fixed amount of magnesium oleate. Thismaterial was compounded to a specific gravity of about 1.125 usingtungsten. The Shore D hardness of this material (as measured on thecurved surface of the inner cover layer) was about 58-60. 3) DuPont HPFSEP 1313-4®, a copolymer of about 81% ethylene and about 19% acrylicacid, wherein 100% of the acid groups are neutralized with magnesiumions. Further, the copolymer contains a fixed amount of magnesiumoleate. This material was compounded to a specific gravity of about1.125 using tungsten. The Shore D hardness of this material (as measuredon the curved surface of the inner cover layer) was about 58-60.

The centers/cores/layers can also comprise various levels of the threecomponents of the terpolymer as follows: from about 60% to 80% ethylene;from about 8% to 20% by weight of the α,β-unsaturated carboxylic acid;and from about 0% to 25% of the n-alkyl acrylate, preferably 5% to 25%.The terpolymer will also contain an amount of a fatty acid salt,preferably magnesium oleate. These materials are commercially availableunder the trade name DuPont® HPF™. In a preferred embodiment, aterpolymer suitable for the invention will comprise from about 75% to80% by weight ethylene, from about 8% to 12% by weight of acrylic acid,and from about 8% to 17% by weight of n-butyl acrylate, wherein all ofthe carboxylic acid is neutralized with magnesium ions, and comprises atleast 5 phr of magnesium oleate.

In another preferred embodiment, the cover layer will comprise aterpolymer of about 70% to 75% by weight ethylene, about 10.5% by weightacrylic acid, and about 15.5% to 16.5% by weight n-butyl acrylate. Theacrylic acid groups are 100% neutralized with magnesium ions. Theterpolymer will also contain an amount of magnesium oleate. Materialssuitable for use as this layer are sold under the trade name DuPont®HPF™ AD 1027.

In yet another preferred embodiment, the centers/cores/layers comprise acopolymer comprising about 88% by weight of ethylene and about 12% byweight acrylic acid, with 100% of the acrylic acid neutralized bymagnesium ions. The centers/cores/layers may also contain magnesiumoleate. Material suitable for this embodiment was produced by DuPont asexperimental product number SEP 1264-3. Preferably thecenters/cores/layers are adjusted to a target specific gravity of 1.125using inert fillers to adjust the density with minimal effect on theperformance properties of the cover layer. Preferred fillers used forcompounding the centers/cores/layers to the desired specific gravityinclude but are not limited to tungsten, zinc oxide, barium sulfate, andtitanium dioxide.

A first set of intermediate layers were molded onto cores using DuPont®HPF™ AD1027, which is a terpolymer of about 73% to 74% ethylene, about10.5% acrylic acid, and about 15.5% to 16.5% n-butyl acrylate, wherein100% of the acid groups are neutralized with magnesium ions. Further,the terpolymer contains a fixed amount of greater than 5 phr magnesiumoleate. This material is compounded to a specific gravity of about 1.125using barium sulfate and titanium dioxide. The Shore D hardness of thismaterial (as measured on the curved surface of the inner cover layer) isabout 58-60.

A second set of layers were molded onto each of the experimental coresusing DuPont experimental HPF™ SEP 1264-3, which is a copolymer of about88% ethylene and about 12% acrylic acid, wherein 100% of the acid groupsare neutralized with magnesium ions. Further, the copolymer contains afixed amount of at least 5 phr magnesium oleate. This material iscompounded to a specific gravity of about 1.125 using zinc oxide. TheShore D hardness of this material (as measured on the curved surface ofthe inner cover layer) is about 61-64.

A first set of covers were molded onto each of the center/layercomponents using DuPont HPF™ 1000, which is a terpolymer of about 75% to76% ethylene, about 8.5% acrylic acid, and about 15.5% to 16.5% n-butylacrylate, wherein 100% of the acid groups are neutralized with magnesiumions. Further, the terpolymer contains a fixed amount of at least 5 phrof magnesium stearate. This material is compounded to a target specificgravity of about 1.125 using barium sulfate and titanium dioxide. TheShore D hardness of this material (as measured on the curved surface ofthe molded golf ball) is about 60-62.

In one embodiment, the formation of a golf ball starts with forming thecenter or inner core. The inner core, intermediate layers, and the coverare formed by compression molding, by injection molding, or by casting.These methods of forming centers, intermediate layers and covers of thistype are well known in the art. The materials used for the center andouter core, as well as the cover, are selected so that the desiredplaying characteristics of the ball are achieved. The center and outercore materials have substantially different material properties so thatthere is a predetermined relationship between the center and outer corematerials, to achieve the desired playing characteristics of the ball.

In one embodiment, the center is formed of a first material having afirst Shore D hardness, a first elastic modulus, a first specificgravity, and a first Bashore resilience. The outer core or intermediatelayer is formed of a second material having a second Shore D hardness, asecond elastic modulus, a second specific gravity, and a second Bashoreresilience. Preferably, the material property of the first materialequals at least one selected from the group consisting of the firstShore D hardness differing from the second Shore D hardness by at least10 points, the first elastic modulus differing from the second elasticmodulus by at least 10%, the first specific gravity differing from thesecond specific gravity by at least 0.1, or a first Bashore resiliencediffering from the second Bashore resilience by at least 10%. It is morepreferred that the first material have all of these material propertyrelationships.

Moreover, it is preferred that the first material has the first Shore Dhardness between about 30 and about 80, the first elastic modulusbetween about 5,000 psi and about 100,000 psi, the first specificgravity between about 0.8 and about 1.6, and the first Bashoreresilience greater than 30%.

In another embodiment, the first Shore D hardness is less than thesecond Shore D hardness, the first elastic modulus is less than thesecond elastic modulus, the first specific gravity is less than thesecond specific gravity, and the first Bashore resilience is less thanthe second Bashore resilience. In another embodiment, the first materialproperties are greater than the second material properties. Therelationship between the first and second material properties depends onthe desired playability characteristics.

Suitable center and outer core materials include HNP's neutralized withorganic fatty acids and salts thereof, metal cations, or a combinationof both, thermosets, such as rubber, polybutadiene, polyisoprene;thermoplastics, such as ionomer resins, polyamides or polyesters; orthermoplastic elastomers. Suitable thermoplastic elastomers includePEBAX®, HYTREL®, thermoplastic urethane, and KRATON®, which arecommercially available from Elf-Atochem, DuPont, BF Goodrich, and Shell,respectively. The center and outer core materials can also be formedfrom a castable material. Suitable castable materials include, but arenot limited to, urethane, urea, epoxy, diols, or curatives.

The cover is selected from conventional materials used as golf ballcovers based on the desired performance characteristics. The cover maybe comprised of one or more layers. Cover materials such as ionomerresins, blends of ionomer resins, thermoplastic or thermoset urethanes,and balata, can be used as known in the art and discussed above. Inother embodiments, additional layers may be added to those mentionedabove or the existing layers may be formed by multiple materials.

When the center is formed with a fluid-filled center, the center isformed first an intermediate layer is molded around the center.Conventional molding techniques can be used for this operation. Then theouter core and cover are formed thereon, as discussed above. The fluidwithin the center core can be a wide variety of materials including air,water solutions, liquids, gels, foams, hot-melts, other fluid materialsand combinations thereof. The fluid is varied to modify the performanceparameters of the ball, such as the moment of inertia or the spin decayrate. Examples of suitable liquids include either solutions such as saltin water, corn syrup, salt in water and corn syrup, glycol and water oroils. The liquid can further include pastes, colloidal suspensions, suchas clay, barytes, carbon black in water or other liquid, or salt inwater/glycol mixtures. Examples of suitable gels include water gelatingels, hydrogels, water/methyl cellulose gels and gels comprised ofcopolymer rubber based materials such a styrene-butadiene-styrene rubberand paraffinic and/or naphthenic oil. Examples of suitable melts includewaxes and hot melts. Hot-melts are materials which at or about normalroom temperatures are solid but at elevated temperatures become liquid.A high melting temperature is desirable since the liquid core is heatedto high temperatures during the molding of the inner core, outer core,and the cover. The liquid can be a reactive liquid system, whichcombines to form a solid. Examples of suitable reactive liquids aresilicate gels, agar gels, peroxide cured polyester resins, two partepoxy resin systems and peroxide cured liquid polybutadiene rubbercompositions.

The “effective compression constant,” which is designated EC, is theratio of deflection of a 1.50 inch diameter sphere made of any singlematerial used in the core under a 100 kg load that as represented by theformula EC=F/d, where, F is a 100 kg load; and d is the deflection inmillimeters. If the sphere tested is only inner core material, theeffective compression constant for the inner core material alone isdesignated EC_(IC). If the sphere tested is only outer core material,the effective compression constant for the outer core material alone isdesignated EC_(OC). The sum of the constants for the inner core EC_(IC)and outer core EC_(OC) is the constant EC_(S). If the sphere tested isinner and outer core material, the core effective compression constantis designated EC_(C). It is has been determined that very favorablecores are formed when their core effective compression constant EC_(C)is less than the sum of the effective compression constants of the innercore and outer core EC_(S). It is recommended that the core effectivecompression constant EC_(C) is less than about 90% of the sum of theeffective compression constants of the inner core and outer core ECS.More preferably, the core effective compression constant EC_(C) is lessthan or equal to about 50% of the sum of the effective compressionconstants of the inner core and outer core EC_(S). The ratios of theinner core material to outer core material and the geometry of the innercore to the outer core are selected to achieve these core effectivecompression constants.

The resultant golf balls typically have a coefficient of restitution ofgreater than about 0.7, preferably greater than about 0.75, and morepreferably greater than about 0.78. The golf balls also typically havean Atti compression of at least about 40, preferably from about 50 to120, and more preferably from about 60 to 100. The golf ball curedpolybutadiene material typically has a hardness of at least about 15Shore A, preferably between about 30 Shore A and 80 Shore D, morepreferably between about 50 Shore A and 60 Shore D.

In addition to the HNP's neutralized with organic fatty acids and saltsthereof, core compositions may comprise at least one rubber materialhaving a resilience index of at least about 40. Preferably theresilience index is at least about 50. Polymers that produce resilientgolf balls and, therefore, are suitable for the present invention,include but are not limited to CB23, CB22, commercially available fromof Bayer Corp. of Orange, Tex., BR60, commercially available fromEnichem of Italy, and 1207G, commercially available from Goodyear Corp.of Akron, Ohio.

Additionally, the unvulcanized rubber, such as polybutadiene, in golfballs prepared according to the invention typically has a Mooneyviscosity of between about 40 and about 80, more preferably, betweenabout 45 and about 65, and most preferably, between about 45 and about55. Mooney viscosity is typically measured according to ASTM-D1646.

When golf balls are prepared according to the invention, they typicallywill have dimple coverage greater than about 60 percent, preferablygreater than about 65 percent, and more preferably greater than about 75percent. The flexural modulus of the cover on the golf balls, asmeasured by ASTM method D6272-98, Procedure B, is typically greater thanabout 500 psi, and is preferably from about 500 psi to 150,000 psi. Asdiscussed herein, the outer cover layer is preferably formed from arelatively soft polyurethane material. In particular, the material ofthe outer cover layer should have a material hardness, as measured byASTM-D2240, less than about 45 Shore D, preferably less than about 40Shore D, more preferably between about 25 and about 40 Shore D, and mostpreferably between about 30 and about 40 Shore D. The casing preferablyhas a material hardness of less than about 70 Shore D, more preferablybetween about 30 and about 70 Shore D, and most preferably, betweenabout 50 and about 65 Shore D.

In a preferred embodiment, the intermediate layer material hardness isbetween about 40 and about 70 Shore D and the outer cover layer materialhardness is less than about 40 Shore D. In a more preferred embodiment,a ratio of the intermediate layer material hardness to the outer coverlayer material hardness is greater than 1.5.

It should be understood, especially to one of ordinary skill in the art,that there is a fundamental difference between “material hardness” and“hardness, as measured directly on a golf ball.” Material hardness isdefined by the procedure set forth in ASTM-D2240 and generally involvesmeasuring the hardness of a flat “slab” or “button” formed of thematerial of which the hardness is to be measured. Hardness, whenmeasured directly on a golf ball (or other spherical surface) is acompletely different measurement and, therefore, results in a differenthardness value. This difference results from a number of factorsincluding, but not limited to, ball construction (i.e., core type,number of core and/or cover layers, etc.), ball (or sphere) diameter,and the material composition of adjacent layers. It should also beunderstood that the two measurement techniques are not linearly relatedand, therefore, one hardness value cannot easily be correlated to theother.

In one embodiment, the center of the present invention has an Atticompression of between about 50 and about 90, more preferably, betweenabout 60 and about 85, and most preferably, between about 65 and about85. The overall outer diameter (“OD”) of the center is less than about1.590 inches, preferably, no greater than 1.580 inches, more preferablybetween about 1.540 inches and about 1.580 inches, and most preferablybetween about 1.525 inches to about 1.570 inches. The OD of the casingof the golf balls of the present invention is preferably between 1.580inches and about 1.640 inches, more preferably between about 1.590inches to about 1.630 inches, and most preferably between about 1.600inches to about 1.630 inches.

The present multilayer golf ball can have an overall diameter of anysize. Although the United States Golf Association (“USGA”)specifications limit the minimum size of a competition golf ball to1.680 inches. There is no specification as to the maximum diameter. Golfballs of any size, however, can be used for recreational play. Thepreferred diameter of the present golf balls is from about 1.680 inchesto about 1.800 inches. The more preferred diameter is from about 1.680inches to about 1.760 inches. The most preferred diameter is about 1.680inches to about 1.740 inches.

The golf balls of the present invention may have a moment of inertia(“MOI”) of about 70-95 g.cm², preferably 75-93, more preferably about76-90 if a lower moment of ? golf ball is desired, the MOI should begreater than 85, preferably greater than 83. For a high MOI ball, theMOI should be less than 86, preferably less than 89. The MOI istypically measured on model number MOI-005-104 Moment of InertiaInstrument manufactured by Inertia Dynamics of Collinsville, Conn. Theinstrument is plugged into a PC for communication via a COMM port and isdriven by MOI Instrument Software version #1.2.

U.S. Pat. Nos. 6,193,619; 6,207,784; and 6,221,960, and U.S. applicationSer. Nos. 09/594,031, filed Jun. 15, 2000; 09/677,871, filed Oct. 3,2000, and 09/447,652, filed Nov. 23, 1999, are incorporated in theirentirety herein by express reference thereto.

The highly-neutralized polymers of the present invention may also beused in golf equipment, in particular, inserts for golf clubs, such asputters, irons, and woods, and in golf shoes and components thereof.

As yet another embodiment, the core comprises a reaction product thatincludes a cis-to-trans catalyst, a resilient polymer component havingpolybutadiene, a free radical source, and optionally, a crosslinkingagent, a filler, or both. Preferably, the polybutadiene reaction productis used to form at least a portion of the core of the golf ball, andfurther discussion below relates to this embodiment for preparing thecore. Preferably, the reaction product has a first dynamic stiffnessmeasured at −50° C. that is less than about 130 percent of a seconddynamic stiffness measured at 0° C. More preferably, the first dynamicstiffness is less than about 125 percent of the second dynamicstiffness. Most preferably, the first dynamic stiffness is less thanabout 110 percent of the second dynamic stiffness.

The cis-to-trans conversion requires the presence of a cis-to-transcatalyst, such as an organosulfur or metal-containing organosulfurcompound, a substituted or unsubstituted aromatic organic compound thatdoes not contain sulfur or metal, an inorganic sulfide compound, anaromatic organometallic compound, or mixtures thereof. The cis-to-transcatalyst component may include one or more of the cis-to-trans catalystsdescribed herein. For example, the cis-to-trans catalyst may be a blendof an organosulfur component and an inorganic sulfide component.

The preferred organosulfur components include 4,4′-diphenyl disulfide,4,4′-ditolyl disulfide, or 2,2′-benzamido diphenyl disulfide, or amixture thereof. An additional preferred organosulfur componentsinclude, but are not limited to, pentachlorothiophenol, zincpentachlorothiophenol, non-metal salts of pentachlorothiophenol such asammonium salt of pentachlorothiophenol magnesium pentachlorothiophenol,cobalt pentachlorothiophenol, pentafluorothiophenol, zincpentafluorothiophenol, and blends thereof. Preferred candidates arepentachlorothiophenol (available from Strucktol Company of Stow, Ohio),zinc pentachlorothiophenol (available from eChinachem of San Francisco,Calif.), and blends thereof. Additional examples are described incommonly-owned copending U.S. patent application Ser. No. 10/882,130,which is incorporated herein by reference in its entirety.

The organosulfur cis-to-trans catalyst, when present, is preferablypresent in an amount sufficient to produce the reaction product so as tocontain at least about 12 percent trans-polybutadiene isomer, buttypically is greater than about 32 percent trans-polybutadiene isomerbased on the total resilient polymer component. In another embodiment,metal-containing organosulfur components can be used according to theinvention. Suitable metal-containing organosulfur components include,but are not limited to, cadmium, copper, lead, and tellurium analogs ofdiethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof. Additional suitableexamples of can be found in commonly owned and co-pending U.S. patentapplication Ser. No. 10/402,592.

Suitable substituted or unsubstituted aromatic organic components thatdo not include sulfur or a metal include, but are not limited to,4,4′-diphenyl acetylene, azobenzene, or a mixture thereof. The aromaticorganic group preferably ranges in size from C₆ to C₂₀, and morepreferably from C₆ to C₁₀. Suitable inorganic sulfide componentsinclude, but are not limited to titanium sulfide, manganese sulfide, andsulfide analogs of iron, calcium, cobalt, molybdenum, tungsten, copper,selenium, yttrium, zinc, tin, and bismuth.

The cis-to-trans catalyst can also include a Group VIA component.Elemental sulfur and polymeric sulfur are commercially available from,e.g., Elastochem, Inc. of Chardon, Ohio. Exemplary sulfur catalystcompounds include PB(RM-S)-80 elemental sulfur and PB(CRST)-65 polymericsulfur, each of which is available from Elastochem, Inc. An exemplarytellurium catalyst under the trade name TELLOY and an exemplary seleniumcatalyst under the tradename VANDEX are each commercially available fromRT Vanderbilt.

A free-radical source, often alternatively referred to as a free-radicalinitiator, is required in the composition and method. The free-radicalsource is typically a peroxide, and preferably an organic peroxide.Suitable free-radical sources include di-t-amyl peroxide,di(2-t-butyl-peroxyisopropyl)benzene peroxide, 3,3,5-trimethylcyclohexane, a-a bis(t-butylperoxy) diisopropylbenzene,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide,di-t-butyl peroxide, 2,5-di-(t-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(t-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, t-butyl hydroperoxide, and the like, and any mixture thereof.

A crosslinking agent is included to increase the hardness of thereaction product. Suitable crosslinking agents include one or moremetallic salts of unsaturated fatty acids or monocarboxylic acids, suchas zinc, aluminum, sodium, lithium, nickel, calcium, or magnesiumacrylate salts, and the like, and mixtures thereof. Preferred acrylatesinclude zinc acrylate, zinc diacrylate (ZDA), zinc methacrylate, andzinc dimethacrylate (ZDMA), and mixtures thereof. The crosslinking agentmust be present in an amount sufficient to crosslink a portion of thechains of polymers in the resilient polymer component. For example, thedesired compression may be obtained by adjusting the amount ofcrosslinking. This may be achieved, for example, by altering the typeand amount of crosslinking agent, a method well-known to those ofordinary skill in the art.

The compositions of the present invention may also include fillers,added to the polybutadiene material to adjust the density and/orspecific gravity of the core or to the cover. Fillers are typicallypolymeric or mineral particles. Exemplary fillers include precipitatedhydrated silica, clay, talc, asbestos, glass fibers, aramid fibers,mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone,silicates, silicon carbide, diatomaceous earth, polyvinyl chloride,carbonates such as calcium carbonate and magnesium carbonate, metalssuch as titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron,lead, copper, boron, cobalt, beryllium, zinc, and tin, metal alloys suchas steel, brass, bronze, boron carbide whiskers, and tungsten carbidewhiskers, metal oxides such as zinc oxide, iron oxide, aluminum oxide,titanium oxide, magnesium oxide, and zirconium oxide, particulatecarbonaceous materials such as graphite, carbon black, cotton flock,natural bitumen, cellulose flock, and leather fiber, micro balloons suchas glass and ceramic, fly ash, and combinations thereof.

Antioxidants may also optionally be included in the polybutadienematerial in the centers produced according to the present invention.Antioxidants are compounds that can inhibit or prevent the oxidativedegradation of the polybutadiene. Antioxidants useful in the presentinvention include, but are not limited to, dihydroquinolineantioxidants, amine type antioxidants, and phenolic type antioxidants.

Other optional ingredients, such as accelerators, e.g.,tetramethylthiuram, peptizers, processing aids, processing oils,plasticizers, dyes and pigments, as well as other additives well knownto those of ordinary skill in the art may also be used in the presentinvention in amounts sufficient to achieve the purpose for which theyare typically used.

The PGA compression of the core, or portion of the core, of golf ballsprepared according to the invention is typically from about 160 or lessas measured on a sphere, preferably about 10 to about 150, morepreferably about 15 to about 140 and most preferably about 20 to about120. Various equivalent methods of measuring compression exist. Forexample, a 70 Atti compression (also previously referred to as the “PGACompression”) is equivalent to a center hardness of 3.2 mm deflectionunder a 100 kg load and a “spring constant” of 36 Kgf/mm. In oneembodiment, the golf ball core has a deflection of about 3.3 mm to 7 mmunder a 130 kg-10 kg test. The various methods for measuring compressionare discussed in the J. Dalton paper, discussed above.

Any of the suitable core materials discussed above can be used in anyother layers on the ball.

The intermediate layers may comprise materials such as thermosettingpolybutadiene or other diene rubber based formulations, thermoplastic orthermosetting polyurethanes, polyureas, partially or fully neutralizedHNP, polyolefins including metallocene or other single site catalyzedpolymers, polymers comprising silicone, polyamides, polyesters,polyether amides, and polyester amides. Suitable thicknesses of theintermediate layers are discussed above.

The outer cover may also comprise a polybutadiene, a cross-linkingagent, a free radical source, and high specific gravity fillers. Anexample of such polybutadiene-based material is as follows:

-   -   100 parts polybutadiene polymer,    -   5-10 parts metal acrylate or methacrylate cross-linking agent,    -   5 parts zinc oxide as the density modifying material,    -   2 parts dicumyl peroxide as the free radical source, and    -   X part(s) metal powder filler, such as tungsten or other heavy        metals, wherein X depends on the desired specific gravity of the        batch and wherein X is a number, integers and real numbers,

In a preferred embodiment, the outer cover layer comprises an HNP thatis a fully neutralized polymer with ions such as Mg, Na, Zn, Li, K, Caor mixtures thereof, and one or more of a fatty acid including oleicacid, stearic acid or behenic acid, or the magnesium salt thereof. Thesematerials are commercially available from DuPont as HPF 1000 or 2000 andas neat spheres have COR of 0.800 to 0.853, and Shore D hardness of 48to 51.

The multi-layer golf ball in this invention is different from previousgolf balls which tend to have a relatively fast core and either (a) afaster inner cover layer and a slower outer cover such as thoseexemplified by the Titleist golf balls, or (b) a slower inner cover anda faster outer cover layer such as those exemplified by the Titleistgolf balls and Newing golf balls, etc. There are other dual core golfballs that have a mixed velocity gradient, but there is no progressivelyincreasing COR values from the center to the cover layer. In thisinvention, the use of relatively slow core allows for more resilientmaterials in each successive center-intermediate layer. Specifically,the multi-layer golf ball will produce a greater loss of COR withincreasing swing speed than a conventional golf ball. The centermaterials with lowest coefficient of restitution come increasingly intoplay as the swing speed and therefore deformation increases. While inthe prior art this could only be achieved by using progressively stiffermaterials, there are now extremely resilient, low flex modulus materialsthat can be used for intermediate layers and the cover layer to make upfor the low-resilient innermost cover. Therefore, the invention relatesto the construction of new and improved golf balls having novelplayability benefits and having COR values that are more beneficial tospecific swing speeds than existing golf balls.

Data illustrating the novel construction of the present inventioncompared to existing golf balls is shown below.

TABLE V COMPARATIVE FOUR-LAYER SAMPLES [CoR(C) − [CoR(C1) − [CoR(C2) −CoR(C) − CoR(C1) − CoR(C2) − CoR(C1)]/ CoR(C2)]/ CoR(C3)]/ Ball NameSizes (in) CoR(C) CoR(C1) CoR(C2) CoR(C3) T(C1) × 10⁻³ T(C2) × 10⁻³T(C3) × 10⁻³ Nike One 1.395/1.487/ 0.824 0.007 0.002 0.007 0.152 0.0390.152 1.590/1.682 Titleist 4 1.000/1.549/ 0.765 −0.040 −0.009 0.006−0.145 −0.250 0.194 Piece 1.619/1.681 COMPARATIVE 3-LAYER SAMPLES ANDINVENTIVE SAMPLE Sizes (in) CoR(C) − CoR(C1) − [CoR(C) − CoR(C1)]/[CoR(C1) − CoR(C2)]/ Ball Name Center/Inter./Cover CoR(C) CoR(C1)CoR(C2) [T(C) − T(C1)] × 10⁻³ [T(C1) − T(C2)] × 10⁻³ Newing EZ1.390/1.522/1.683 0.756 −0.007 −0.042 −0.106 −0.519 Drive Hibrid1.448/1.558/1.683 0.754 −0.010 −0.031 −0.182 −0.492 Everio Taylormade1.487/1.582/1.684 0.771 −0.002 −0.017 −0.042 −0.340 Inergel Pro DistanceTour Special 1.389/1.539/1.681 0.766 −0.019 −0.013 −0.253 −0.183 MetalMix Strata 1.481/1.572/1.681 0.770 −0.006 −0.010 −0.130 −0.182Professional Control Super 1.437/1.568/1.681 0.780 −0.011 −0.013 −0.167−0.228 Newing Maxfli EXT 1.479/1.580/1.684 0.799 −0.008 −0.009 −0.157−0.180 Titleist 3 Piece 1.549/1.620/1.681 0.803 −0.012 0.007 −0.3330.222 Inventive 1.530/1.620/1.681 0.780 −0.015 −0.015 −0.333 −0.484Where C = subassembly containing the center; C1 = subassembly containingthe center and intermediate layer; C2 = subassembly containing thecenter and two intermediate layers or a three-layer ball; and C3 = ballwith all four layers.

Unless otherwise expressly specified, all of the numerical ranges,amounts, values and percentages such as those for amounts of materials,and others in the specification may be read as if prefaced by the word“about” even though the term “about” may not expressly appear with thevalue, amount or range. Accordingly, unless indicated to the contrary,the numerical parameters set forth in the specification and attachedclaims are approximations that may vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

While it is apparent that the illustrative embodiments of the inventiondisclosed herein fulfill the preferred embodiments of the presentinvention, it is appreciated that numerous modifications and otherembodiments may be devised by those skilled in the art. Examples of suchmodifications include slight variations of the numerical valuesdiscussed above. Hence, the numerical values stated above and claimedbelow specifically include those values and the values that areapproximately or nearly close to the stated and claimed values.Therefore, it will be understood that the appended claims are intendedto cover all such modifications and embodiments, which would come withinthe spirit and scope of the present invention.

1. A multi-layer golf ball comprising a center, a cover layer, and atleast two intermediate layers between the center and the cover layer,wherein each subassembly of the golf ball has a combined coefficient ofrestitution value that is less than the combined coefficient ofrestitution of said subassembly plus the next outer layer by a value ofat least 0.003, wherein the subassembly comprises at least the center,and wherein the center has a coefficient of restitution value of lessthan 0.800.
 2. The multi-layer golf ball of claim 1, wherein eachsubassembly has a combined coefficient of restitution value that is lessthan the combined coefficient of restitution of said subassembly plusthe next outer layer by a value of at least 0.005.
 3. The multi-layergolf ball of claim 1, wherein each subassembly as a combined coefficientof restitution value that is less than the combined coefficient ofrestitution of said subassembly plus the next outer layer by a value ofat least 0.010.
 4. The multi-layer golf ball of claim 1, wherein theintermediate layers comprises eight layers or less.
 5. The multi-layergolf ball of claim 1, wherein the center has a coefficient ofrestitution value of less than 0.780.
 6. The multi-layer golf ball ofclaim 1, wherein the subassembly represented by the center and the firstintermediate layer has a combined coefficient of restitution value of atleast 0.780.
 7. The multi-layer golf ball of claim 1, wherein thesubassembly represented by the center and the first intermediate layerhas a combined coefficient of restitution value of at least 0.790. 8.The multi-layer golf ball of claim 1, wherein the subassemblyrepresented by the center, the first intermediate layer, and the secondintermediate layer has a combined coefficient of restitution value of atleast 0.790.
 9. The multi-layer golf ball of claim 5, wherein thesubassembly represented by the center, the first intermediate layer, andthe second intermediate layer has a combined coefficient of restitutionvalue of at least 0.800.
 10. The multi-layer golf ball of claim 1,wherein the golf ball has a combined coefficient of restitution value ofat least 0.800.
 11. The multi-layer golf ball of claim 1, wherein thegolf ball has a combined coefficient of restitution value of at least0.805.
 12. The multi-layer golf ball of claim 1, wherein the centercomprises a material selected from the group consisting of apolybutadiene, a polyurethane, a polyurca, a highly neutralized polymer,a silicone, a polyolefin, a polyamide, a polyester, a polyether amide, apolyester amide, and a blend thereof.
 13. The multi-layer golf ball ofclaim 1, wherein the intermediate layers comprise a member selected fromthe group consisting of a polybutadiene, a polyurethane, a polyurea, ahighly neutralized polymer, a silicone, a polyolefin, a polyamide, apolyester, a polyether amide, a polyester amide, and a blend thereof.14. The multi-layer golf ball of claim 1, wherein the cover layercomprises a highly neutralized polymer formed from a reaction betweenacid groups on the polymer, a suitable source of cation, and an organicacid or the corresponding salt, and the amount of the suitable cation issufficient to neutralize the acid groups by least 80%.
 15. Themulti-layer golf ball of claim 14, wherein the amount of the suitablecation is sufficient to neutralize the acid groups by least 90%.
 16. Themulti-layer golf ball of claim 14, wherein the amount of the suitablecation is sufficient to neutralize the acid groups by about 100%,wherein the suitable source of cation is selected from the groupconsisting of magnesium, sodium, zinc, lithium, potassium and calcium,and wherein the organic acid or the corresponding salt is selected fromthe group consisting of oleic acid, salt of oleic acid, stearic acid,salt of stearic acid, behenic acid, salt of behenie acid and combinationthereof.
 17. The multi-layer golf bail of claim 1, wherein the coverlayer is a product of a reaction mixture comprising a polybutadiene, acis-to-trans catalyst, a free radical source, a crosslinking agent, anda filler.
 18. A multi-layer golf ball comprising a center, a coverlayer, and at least two intermediate layers between the center and thecover layer, wherein each subassembly of the golf ball has a combinedcoefficient of restitution value that is less than the combinedcoefficient of restitution of said subassembly plus the next outer layerby a value of at least 0.003, wherein the subassembly comprises at leastthe center, and wherein the change in coefficient of restitution fromone subassembly to the next larger assembly per the thickness of thenext larger subassembly is less than 0.00010 per thousandth of an inch.19. The multi-layer golf ball of claim 18, wherein said change incoefficient of restitution is less than about 0.00020 per thousandth ofan inch.
 20. The multi-layer golf ball of claim 18, wherein said changein coefficient of restitution is less than about 0.00030 per thousandthof an inch.
 21. A multi-layer golf ball comprising a center, a coverlayer, and an intermediate layer between the core and the cover layer,wherein each subassembly of the golf ball has a combined coefficient ofrestitution value that is less than the combined coefficient ofrestitution of said subassembly plus the next outer layer by a value ofat least 0.015, wherein the subassembly comprises at least the center,and wherein the change in coefficient of restitution from onesubassembly to the next larger assembly per the thickness of the nextlarger subassembly is less than 0.00020 per thousandth of an inch. 22.The multi-layer golf ball of claim 21, wherein each subassembly has acombined coefficient of restitution value that is less than the combinedcoefficient of restitution of said subassembly plus the next outer layerby a value of at least 0.018.
 23. The multi-layer golf ball of claim 22,wherein each subassembly as a combined coefficient of restitution valuethat is less than the combined coefficient of restitution of saidsubassembly plus the next outer layer by a value of at least 0.020. 24.The multi-layer golf ball of claim 21, wherein said change incoefficient of restitution is less than about 0.00030 per thousandth ofan inch.
 25. The multi-layer golf ball of claim 21, wherein said changein coefficient of restitution is less than about 0.00040 per thousandthof an inch.